Heavy Flow Period Kit

 

When it comes to protection, this kit is a heavy-hitter. 7 best-selling styles for teens who want 100% protection on heavy days, heavy nights, and when they can’t frequently change their pad or tampon.

What You Get:
- 6 Super Leakproof™ Underwear in Black* Each pair absorbs about 3 super tampons' or 1.5 regular pads' worth of blood.
- 1 Super Leakproof™ Sleepover Short in Black Absorbs 5.5 super tampons' or 2.5 regular pads' worth of blood.
- 1 Reusable Pouch


*In your choice of Bikini, Boyshort, or High Rise.

Their heaviest days are no match for our most-absorbent kit ever.
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Period protection that holds between 3-5.5 super tampons’ worth of blood
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Designed to feel just like regular underwear
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Rapidly absorbs moisture to keep you fresh and dry all day
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Sleepover Short features a longer gusset to prevent leaks all night

 

When it comes to protection, this kit is a heavy-hitter. 7 best-selling styles for teens who want 100% protection on heavy days, heavy nights, and when they can’t frequently change their pad or tampon.

What You Get:
- 6 Super Leakproof™ Underwear in Black* Each pair absorbs about 3 super tampons' or 1.5 regular pads' worth of blood.
- 1 Super Leakproof™ Sleepover Short in Black Absorbs 5.5 super tampons' or 2.5 regular pads' worth of blood.
- 1 Reusable Pouch


*In your choice of Bikini, Boyshort, or High Rise.

Super Leakproof Underwear

Body: 70% Nylon, 30% Spandex 

Lining: 84% Modal, 8% Seaweed, 8% Spandex 

Gusset: Leakproof Technology®, 100% Polyester, PU Film


Machine wash cold with mild detergent, do not bleach, tumble dry on low. 


Super Leakproof Sleepover Short

Body: 70% Nylon, 30% Spandex 

Lining: 84% Modal, 8% Seaweed, 8% Spandex 

Gusset: Leakproof Technology®, 100% Polyester, PU Film 


Machine wash cold with mild detergent, do not bleach, tumble dry on low.


Additional Product Ingredient Information

For items with a 20% or more discount, you may exchange for another item or return for store credit. No refunds can be accommodated. 

Items marked as “Flash Sale” or “Clearance” are final sale, meaning no returns, exchanges or refunds can be accommodated. No exceptions. 

Please note: Sale items are not eligible for our First Pair Risk-Free Policy.

We offer free standard shipping on all orders over $70. We ship our items via DHL or Canada Post depending on your location. Please allow 1-2 business days for your items to be processed and shipped. During high volume periods, your order may take up to 7 business days to dispatch from our warehouse location.


US Orders: Please allow 3–10 business days for orders to arrive.
International Orders: Please allow 10–25 business days for orders to arrive.


NOTE: Orders placed on Friday after 1 PM will not be processed until the following Monday.
CANADIAN CUSTOMERS: Shop www.knixteen.ca to order in Canadian currency.

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Super Absorbency

Absorbs 9–12 tsp (45–60 ml) of blood—that’s about 9–12 regular tampons or pads! Perfect for overnight protection or your heaviest days when changing into a fresh pair might not be convenient.


High Absorbency

Absorbs 4–8 tsp (20–40 ml) of blood, or the equivalent of 4–8 tampons or pads. These are perfect for heavy flow days.


Medium Absorbency

Absorbs up to 3 tsp (15 ml), or about 3 tampons or pads worth of blood. Ideal for light to medium flow days or as backup to tampons or period cups.

All of our period underwear, swimwear, reusable pads, and activewear have our patented leakproof technology built right in.

First Layer: Moisture-wicking, antibacterial technology wicks away sweat and moisture while neutralizing odors to keep you fresh all day long. 

Second Layer: A super thin, highly absorbent liner that holds the power of 3–20 tampons or pads.

Third Layer: A secure, liquid-resistant outer layer keeps leaks from happening.

The short answer: nope! Depending on the absorbency level of your period underwear and the heaviness of your flow, you can wear our period undies on their own or as a backup to tampons or menstrual cups. You can wear our High and Super absorbency underwear alone and be totally protected, while our Medium absorbency underwear can be worn alone on lighter days or as backup on heavier days.

Step 1: Give your underwear a quick rinse under cold water.
Step 2: Throw it in the washing machine with your regular clothes. Wash on cold with mild detergent (no softener or bleach).
Step 3: There are two ways to dry them depending on the undies you have: lay flat to dry for medium absorbency products, or tumble dry on low for high to super absorbency products.
Step 4: That’s it! No ironing needed.

Check out our size chart here. If you want some help, we have virtual fitters ready on deck to help you find your perfect fit. Book a video call with them today.

Because they’re, well, underwear, we can’t accept exchanges or returns on used items. BUT you can try your first pair on your first order risk-free for 30 days!


If you ordered the wrong size of period underwear, we’ll send you a different pair at no cost or offer you a standard refund within 30 days of delivery (excluding original shipping fees).


If your order included multiple period underwear, open, wash, and wear one pair only. That way if you don’t love them, any unopened packages from the same purchase will be eligible for an exchange or standard refund (excluding original shipping fees).


All unopened packages will be donated to local organizations to support people in need.


*All Mystery Bundles are final sale.

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COMFORTABLE
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ABSORBENT
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JUST PLAIN BETTER
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REUSABLE
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COMFORTABLE
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ABSORBENT
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JUST PLAIN BETTER
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REUSABLE
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COMFORTABLE
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ABSORBENT
Image of a chrome heart surrounding text
JUST PLAIN BETTER
Image of a chrome heart surrounding text
REUSABLE
Image of a chrome heart surrounding text
COMFORTABLE
Image of a chrome heart surrounding text
ABSORBENT
Image of a chrome heart surrounding text
JUST PLAIN BETTER
Image of a chrome heart surrounding text
REUSABLE
Image of a chrome heart surrounding text
COMFORTABLE
Image of a chrome heart surrounding text
ABSORBENT
Image of a chrome heart surrounding text
JUST PLAIN BETTER
Image of a chrome heart surrounding text
REUSABLE
Image of a chrome heart surrounding text
COMFORTABLE
Image of a chrome heart surrounding text
ABSORBENT
Image of a chrome heart surrounding text
JUST PLAIN BETTER
Image of a chrome heart surrounding text
REUSABLE
Image of a chrome heart surrounding text
COMFORTABLE
Image of a chrome heart surrounding text
ABSORBENT
Image of a chrome heart surrounding text
JUST PLAIN BETTER
Image of a chrome heart surrounding text
REUSABLE
Image of a chrome heart surrounding text
COMFORTABLE
Image of a chrome heart surrounding text
ABSORBENT
Image of a chrome heart surrounding text
JUST PLAIN BETTER
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REUSABLE
Reviews
average rating 4.4 out of 5
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Review posted
Reviewed by Melissa
Verified Reviewer
Rated 5 out of 5

Best period underwear

We have tried multiple other brands and my daughter is 11 and has heavy periods. The other brands she had to put always pads in with them. But this is the best brand we have found. She love sleep over shorts for overnight no leaks. I bought this package. I had to buy more sleep over shorts. I just purchase boxer briefs super absorancy. She loves and Knixteen products.

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Reviewed by Sandrine V.
Rated 5 out of 5

Excellent achat!

J’ai acheté cet ensemble pour ma fille, qui a ses règles depuis peu. Elle a un flux assez abondant, elle doit souvent changer ses serviettes sanitaires, et elle voyait ses règles comme quelque chose d’extrêmement désagréable. J’ai décidé de lui faire essayer les culottes menstruelles, et elle les adore! Celles-ci sont parfaites pour les règles plus abondantes. La journée la plus abondante de son cycle, elle change de culotte sur l’heure du dîner; mais pour les 6 autres jours, elle utilise la même culotte toute la journée. Elle n’a jamais eu de fuite. Elle adore aussi la paire de boxers de nuit, parce qu’elle avait toujours peur de tacher ses draps la nuit... mais maintenant cela ne l’inquiète plus. Je suis vraiment heureuse de lui avoir fait essayer ce kit. Nous allons certainement en acheter d’autres à l’avenir!

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Reviewed by Victoria
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Rated 5 out of 5

Where has this been all my life?

Have a teen girl who is still shy about her period. This is so much easier for her than changing bulky pads all day. They are comfy and discreet. We got one pair to try and went back for the period kit. She loves her KT! Great for her and so much better for the environment too.

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Reviewed by Christine
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Rated 5 out of 5

Teen Approved

I bought this kit for my daughter who is absolutely in love! She used to go through 3-4 pads a day, but just wears one pair of these Super 'Oh-No' Proof underwear now! It's perfect for her since there's just enough underwear included to get her through the most heavy days of her cycle, plus the shorts for nighttime. Such a great product!

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Reviewed by Jade
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Rated 5 out of 5

The Best Underwear for Heavy Periods

I purchased this kit because I have a HEAVY flow that just won't quit some days. It really works so well! I know all my friends thought it would feel like "sitting in a diaper" but boy are they wrong! The underwear stays dry and comfortable. The kit is such a good deal for the 4 underwear, shorts and pouch too that get me through my entire cycle. Worth it!

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