Frequently Asked Questions

Orders & Shipping

I’ve already submitted my order, but I need to make a change! What do I do? Is it too late?
We process our orders quickly (so you can get your undies fast!), but we will do our best to accommodate any requests you may have. The best way to adjust or cancel an order is to email or call us at (917) 819-8171.
When can I expect to receive my order?
For standard shipping, your order should ship within 1-2 business days (Mon-Fri, before 2 pm), and arrive within 5-7 business days. For expedited shipping, your order should arrive in 3-5 business days (continental U.S. only). If you pre-ordered an item, the shipping date was indicated when you placed your order.
What is your return policy?
Not loving your undies? No worries — we process returns and exchanges within 60 days of purchase, no questions asked (not valid on final sale items, tampons, merch, or gift cards). We will also provide you with a free pre-paid return label. You can request a return or exchange via

If your order qualifies for a return, ...
I live abroad. Can I still order Thinx (BTWN)?
Yes! We offer international shipping so everybody can have the most innovative period solutions.
Does Thinx (BTWN) cover taxes, duty, etc. for international customers?
Unfortunately, our prices don't include local taxes, duties, brokerage fees, VATs, or any other stuff you may be additionally charged to receive your Thinx (BTWN) shipment internationally.

Make sure you consider *all fees* before you place your order because you’ll be required to make those payments when your shipment arrives, and we won’t be able to refund you if you change your mind.
What currencies do you accept?
We love our friends from all around the world, which is why we accept nearly all local currencies. On the off chance we do not accept your local currency, you’ll have the option of checking out in USD, CAD, EUR, AUD, or British Pounds.
I'm having trouble placing my order on your website. Help!
While we do our best to ensure that our e-commerce experience is consistent, enjoyable, and functional across all modern browsers and devices, occasionally something small may not function properly on older browsers when an update to our code is pushed.

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What is a Custom Saver Set?
Custom Saver Sets are a great way for you to stock up and save. Mix and match any styles, colors, and sizes across all our brands (Thinx (BTWN), Thinx and Speax) to take advantage of the following discounts:
  • Buy 3+ pairs and save 10%
  • Buy 5+ pairs and save 15%
  • Buy 7+ pairs and save 20%
This discount will apply automatically in your cart and only applies to full price styles. You can return the items individually if they don’t work out. Fresh Start Period Kits are not eligible for a Custom Saver Set discount.
Can I return or exchange 1 or 2 pairs of underwear from the Fresh Start Period Kit?
The Fresh Start Period Kit is sold as a unit, so you can't return or exchange individual pairs of undies from it — but you can return or exchange the whole kit, no questions asked.
What type of payment do you accept?
We are a cash-free establishment and accept all major credit cards. Thinx gift cards can only be used for online purchases.
Are undies I buy at the pop-up store final sale?
Nope! Unopened and unworn merchandise purchased from our pop-up can be returned or exchanged in store. If you’d like to return items you purchased online, email


How do Thinx (BTWN) work?
Thinx (BTWN) are underwear that absorb menstrual flow, wick moisture, control odors, and prevent leaks. Check out our Product Info page to — you guessed it — learn more about how Thinx (BTWN) work! And if you want to learn more about how *periods* work, we’ve got a page for that, too.
How much liquid can Thinx (BTWN) hold?
The 4 tampon absorbency styles hold up to 36 ml and the 2 tampon absorbency styles hold up to 18 ml. Please refer to the specific product page for more details.
How long can tweens and teens wear Thinx (BTWN)?
For most tweens and teens, our 4 tampon absorbency undies can last between 8 - 12 hours. But every period is different — depending on their flow (light, moderate, heavy), they may have to change their Thinx (BTWN) more often. Pro tip: if they’ve got a long day ahead, pack extra pairs just in case! We suggest each tween or teen try Thinx (BTWN) at home first to understand how it works for their body and period.
What if my child needs to change their Thinx (BTWN) during the day?
Our higher absorbency styles hold up to 4 tampons’ worth, so we recommend them for all-day protection. But depending on their flow, they may need to pack an extra pair of Thinx (BTWN) to get through the day — no big deal! Our undies are lightweight and easy to store, so an extra pair will fit perfectly in any backpack or gym bag. We suggest they bring along a resealable bag, pouch, or wet bag — so that when they do need to change out of their first pair of Thinx (BTWN), they’ve got a place to put it.
Will there be stains on their Thinx (BTWN)?
Nope. The interior of Thinx (BTWN) is lined with black fabric, so they’ll never look down and see stains.
Are Thinx (BTWN) reusable?
Yes! Our period underwear is washable and reusable. Plus, they’re easy to wash, and when cared for properly can last up to 2 years.
Are Thinx (BTWN) a replacement for my child’s current routine?
Depending on their flow (light, moderate, heavy), Thinx (BTWN) can be worn alone or with tampons or cups. On their light days, they can wear the undies instead of pads and panty liners. On heavy days, they can wear them as a backup to tampons or cups for extra protection. We suggest they try Thinx (BTWN) at home first to understand how the undies work for their body and their period.
Can Thinx (BTWN) be worn as a backup to pads and panty liners?
No. Thinx (BTWN) are designed to fit close to the body to help prevent leaks and stains. If someone puts a pad or pantyliner on top of their Thinx (BTWN), the gusset won’t be close enough to the body to absorb their period. For folks who usually wear pads and pantyliners, we recommend wearing 1 or 2 pairs of Thinx (BTWN) throughout the day instead — without anything else. For folks who like to wear tampons, they can wear Thinx (BTWN) with as a backup (tampons don’t take up space outside of the body, so our undies will be close enough to help prevent leaks).
How can you be sure they won’t leak?
Our underwear has been tested by product developers, doctors, and real people just like you — Thinx (BTWN) really does work! But every person and every period is unique, so Thinx (BTWN) helps different people manage their flow in different ways. Some people with heavy flows wear the undies as a backup to other period products, and some people wear them instead of pads and panty liners. We suggest your tween or teen tries them at home first to figure out what’s best for them.
How many pairs of Thinx (BTWN) will my child need?
Some people buy a Fresh Start Period Kit so they have multiple pairs ready to change into, while other people start with just 1 pair and wash it at night before wearing the next day. In the end, it’s up to you and what’s best for your lifestyle and your tween or teen’s flow. (Insider tip: You save $$$ if you buy a Fresh Start Period Kit!)
How do I know which Thinx (BTWN) is the right size for my child?
Our undies are true to classic sizing for girls’ underwear and clothing. Take a peek at our handy sizing chart to get the right measurements for the perfect fit.
Are Thinx (BTWN) hygienic?
Yes! Every pair of underwear is lined with odor-controlling, super-absorbent, and moisture-wicking materials so you always feel fresh and dry.
How do Thinx (BTWN) control odor?
The moisture-wicking layer of our underwear has an application of non-migratory silver, commonly used in performance wear and medical devices to control odor and the spread of bacteria. “Non-migratory” means it won’t come off the undies and that it only responds to bacteria *on the fabric*, not on skin (so the vaginal microbiome stays fresh and balanced!).
How do I wash the underwear?
It's simple! Just machine wash in cold water and hang dry.

Do not use fabric softener, bleach, or irons, as they hurt the absorbent, odor-controlling gusset.
Can Thinx (BTWN) be worn as a swimsuit?
We don’t recommend using these undies as a swimsuit because we can’t guarantee the period absorbency will work in the water.
What are Thinx (BTWN) made of?
The entire gusset is lined with cotton, so only natural fiber touches the most sensitive areas. And the body of each pair of Thinx (BTWN) is made of organic cotton, which is super-cozy and extra-breathable. Here’s the fabric breakdown: outer shell: 95% organic cotton, 5% elastane; inner lining: 95% organic cotton, 5% elastane; middle layers: 95% cotton, 5% elastane, 80% polyester, 20% nylon, breathable.
Where are Thinx (BTWN) manufactured?
Our undies are made by our partners at MAS, a family-run factory in Sri Lanka known for their expertise with intimates. We’re proud to work together because they share the same values we do: empowering women and creating innovative, sustainable period solutions.
Where can I buy Thinx (BTWN)?
Right here! We currently sell our undies exclusively online. Shop all our Thinx (BTWN) styles here.
Why do Thinx (BTWN) cost more than pads and tampons?
Our undies are machine washable, reusable, and absorbent — there’s *a lot* of science and development that goes into making them, and making sure they last. Disposable products can only be used once, but Thinx (BTWN) can last up to 2 years — that means over time you can save serious $$$.
What are Thinx?
Thinx are underwear that absorbs your period, made for adults. Both Thinx and Thinx (BTWN) absorb menstrual flow, wick moisture, control odor, and prevent leaks. Thinx styles are made with taller, curvier adult bodies in mind, and come in a range of absorbency levels — so adults have a variety of stylish options for lighter and heavier days.
What if my child fits both Thinx (BTWN) and Thinx?
Thinx (BTWN) are made for teen and tween body shapes and sizes. Thinx are engineered for adult bodies. If you need help deciding which line is right for your child, drop us a note and we’ll help you find the *perfect* fit.
Do THINX (BTWN) and Thinx have the same absorbency levels?
While Thinx styles offer a variety of absorbency levels from 0.5 to 4 tampons' worth, Thinx (BTWN) styles come in two absorbencies, either 2 tampons' worth or 4 tampons' worth. Because tweens and teens live busy, full lives, and first and early periods can be inconsistent and uneven. These higher-level absorption options help reduce worry about leaks and stains.
What's the difference between Thinx (BTWN) and Thinx styles?
All Thinx (BTWN) undies are full-coverage, provide maximum absorbency, and are specifically designed for tween and teen body shapes and sizes. They’re the perfect choice for early periods, which can be inconsistent. Thinx offers a range of styles for adults — from super-comfy boy shorts to barely-there thongs — with different levels of absorbencies, for folks who know their flow and can pick the perfect fit. See all our Thinx (BTWN) styles to choose what’s right for your child.

Period Info

What exactly is a period, and why do I have one?
The simplest explanation is that a period is when your body releases blood and tissue that it no longer needs through your cervix and vagina. This tissue is a lining in your uterus (where an egg travels from your ovaries during ovulation) that gets thicker in preparation for the egg to be fertilized. When you don’t become pregnant, your body releases both the lining and the unfertilized egg approximately every 21 - 45 days. This is menstruation, or what we call “a period,” and it’s totally natural!
When will I get my period?
*Every body* is different, and it’s no big deal to get your period before or after your friends. Some people get their first period as early as 8 or 9 years old, others get them as late as 16. First periods often happen around the same time in life for people who are related to one another, so if you can, ask your mom or big sister or someone related to you with a period when they got theirs to get some idea of when you’ll get yours.
How will I know if I’ve gotten my period?
Not all periods are red, so you may see some brown or pink fluid in your underwear. Regular vaginal discharge is clear or milky, so if you see something that’s more pink, red, or brown, guess what — you probably just got your period!
All my friends have gotten their period, why haven’t I?
First periods don’t happen at the same time for everyone, and there’s nothing wrong with you if start your period before or after your friends. We asked around in our office and some people got their first periods at 8 years old, others as late as 16 — that’s a big difference! Ask your mom or sister when they got theirs to get a better idea of when your first period will start (yes, first period start dates can be hereditary!).
What does a period feel like?
You may not feel your period flow, instead you’ll just notice some color on your undies. Some people feel a little wetness, more than usual vaginal discharge.
How long does a period last in one month?
The amount of time you’ll bleed every month can vary from 3 to 7 days, but it’s normal for your period to vary a little from cycle to cycle. If you notice blood for longer than 7 days, it’s a good idea to check with your gynecologist to make sure everything is okay.
Will my period hurt?
It shouldn’t. The flow of menstrual fluid out of your vagina shouldn’t hurt at all (you probably won’t even know it’s happening!). Some people get cramps or back aches before they start their period, and those can be uncomfortable, but they shouldn’t be painful. If you are in a lot of pain during your period, set up an appointment with your gynecologist so they can help you feel better — nobody should live with period pain!
Will people know I have my period?
Probably not, unless you tell them. A lot of the signs and symptoms that come with a period are only noticeable to you. But there’s nothing wrong with telling people that you’re on your period, or that you’re feeling a little different because of your period. Sometimes it can make you feel better to talk to family or friends about what’s going on.
Why is my period brown?
Periods come in all different colors and textures — some are more red and liquidy, others may be brown and clumpy. Brown blood is just blood that’s a bit older. Some people notice brown blood before they see red (on or before day 1), others have brown blood at the end of their period (day 5, or whenever your period ends). If you’ve just started your period, you may only see brown stuff, and that’s totally normal. We made a li’l video talking more about this, check it out here.
Sometimes my period is heavy, sometimes it’s light. Why is that?
Periods are different from person to person, and can be different in the same person from cycle to cycle. You may start with a light flow, have heavy days in the middle, and finish off with a light flow; or have heavy flows at the beginning and then lighter days only at the end; or something else! You’ll get to know *your* flow over time and understand what heavy, moderate, and light days mean for you.
Can I swim and play sports on my period?
Absolutely! You can do *anything* on your period—swim, dance, wear white pants, go camping, whatever—you may just want to use different period products depending on the activity.
What do you mean when you say “cycle” and “flow”?
When we refer to your period “cycle” we’re talking about the time from when you first start bleeding (day 1 of your period) to when you stop bleeding (could be day 4, 5, 6, or longer). It can also refer to the 21 - 45 day timeframe between day 1 of your last period and day 1 of your new period. When we talk about your “flow,” we’re referring to the fluid that comes out of your vagina (the red/brown/pink stuff).
What is PMS?
PMS stands for Premenstrual Syndrome and it’s often defined by symptoms you may feel, physically and emotionally, before you get your period. PMS symptoms can include cramps, sore boobs, laziness, moodiness, or an appetite for certain foods (we *always* crave pizza!). A lot of times, PMS symptoms show up a few days before your flow starts and can be helpful signs to let you know to wear your Thinx (BTWN) in preparation for what’s to come.
How do I talk to my mom about my period?
It may feel super-awkward, but it doesn’t have to be (hey, your mom has experienced periods, too!). Sometimes it’s easiest just to blurt this kinda stuff out, but you can also write her a note or send her a text if that feels better to you. And, look, it isn’t just moms who can be helpful with first periods: You can always talk to your dad, cool aunt, big sister, favorite teacher, school nurse, or any other adult you trust to give you support and advice. Remember, periods are 100% normal and nothing to be ashamed about! Watch this video for more tips from us on how to talk to your mom about your period.
How do I hide my period from my mom?
You *could* hide it from your mom, but we don’t recommend it. Why? For a few really important reasons: 1. Periods are nothing to be ashamed of or hide. 2. Your mom can probably give you some really awesome tips on what products to use and how to feel better if you have PMS symptoms. 3. Periods can be a great bonding moment, and your mom will probably make you feel really proud of your body and excited to grow up.
Do boys get periods?
We’re so glad you asked! Not all bodies experience periods, only bodies with uteruses. These bodies produce certain hormones (naturally-occurring chemicals in our bodies) that make a menstrual cycle happen, which is a fancy way of saying that they make a period happen. Bodies without uteruses (such as bodies with penises) don’t experience periods because they don’t have a uterus.
Will I have my period forever?
No. Your period will eventually stop when you enter what’s called menopause. This happens for most people between the ages of 45 and 55, and, like your period, menopause will come with some new physical and emotional changes.


What is your mission?
Our mission is to empower every body* through innovative solutions and social change — and we’re doing that with the products we create and the conversations we start.
How does Thinx (BTWN) help underserved communities?
Giving back to people with periods has been at the core of our mission since day 1 — but we know there’s still a lot of work to do (like more education, accessibility, and resources). That’s why we’re committed to paying it forward through GiveRise, our giveback program. When you purchase from Thinx (BTWN), you're helping to support our programs and initiatives at GiveRise, including the EveryBody education program — our inclusive, medically accurate, and hands-on curriculum designed to educate future generations about their changing bodies in a safe, empowered space.

Want to learn more? Visit our GiveRise page!


Can I sell Thinx, Inc. products in my store?
Thank you for your interest! Our biz is *growing* and because of the massive interest in our innovative underwear, we launched a wholesale channel! If you’re interested in selling our products, head over to our Wholesale Page for more details.

Affiliate Programs

Do you have an affiliate program?
Yes. Our affiliate program is managed through Pepperjam. To apply for the program, please sign up here.


What is Afterpay?
With Afterpay, you can buy Thinx (BTWN) today and pay for your order in 4 equal payments made every 2 weeks — no interest added.
How do I use it?
After adding Thinx (BTWN) to your cart, choose Afterpay at checkout as your payment method. If this is your first time using Afterpay, you'll be redirected to their website to register and give your payment details. If you've used Afterpay before, just log in to your account. Complete your order, and you're all done! Just remember — all items in your cart must be eligible for Afterpay, and the value must be between $35 and $1,000.
Where can I use it?
Afterpay can be used for all purchases at — as well as our sister brands Thinx and Speax. However, it cannot be used at our retail partners or pop-up locations.
Can I use Afterpay if I'm an international customer?
Unfortunately, no — Afterpay is only available to customers in the US
What's the payment schedule like?
With Afterpay, you'll be required to make your first payment at the time of your purchase. The remaining 3 payments will be deducted automatically in equal installments every 2 weeks from the payment method you've set up. If you want to make a payment before your next installment is due, log in to your Afterpay account — your amount owed will be updated accordingly.
What if I can't pay an installment?
Late fees may apply if you cannot make a payment. Take a look at Afterpay's complete terms and conditions for more details.
When will my stuff be delivered if I use Afterpay?
Afterpay orders are sent just like our standard US shipping orders, and should get to you within 5-7 business days. Take a look at our complete shipping details for more information.
Is there a limit to how much I can spend in one Afterpay transaction?
Yes, Afterpay purchases must be between $35 and $1,000.
Can I use another form of payment with Afterpay?
You can also use a gift card with Afterpay to pay for your purchase.
What products are not eligible for Afterpay?
Gift cards are not eligible for Afterpay.
How do I return or exchange something I bought with Afterpay?
You still get our 60-day money-back guarantee if you use Afterpay. If you return an item, we will refund Afterpay and the credit will show up in your Afterpay account. We cannot, however, process an exchange for a purchase made with Afterpay.
Where can I learn more about Afterpay?
Visit the Afterpay website to get answers to all your questions. You can also get help from our customer experience team at