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Bundle Deal

Leakproof UltraThin™ No-Show Bikini Shimmer 3-Pack

$68.00 USD

$81.00

Save $13

New improved fit

Absorbs about 2.5 super tampons

Invisible under clothes

Moderate protection without the bulk

Machine washable

Color: Midnight & Cherry Polka Dot/Cherry/Pink Party Limited Edition

Size:

True to Size

•

Size:

Size and Fit Guide

Free Shipping on orders $100+

Shipping

Shipping

Processing Timelines

Please allow 1-2 business days for our warehouse team to pack and ship your order. During peak periods such as sales, holidays and product launches, please allow up to 4 business days for us to process your order. Once an order is placed, we cannot guarantee any address updates, order changes or cancellations. Orders placed on Friday after 1PM will not be shipped until the following Monday.


Split Shipments

Most orders will ship from a single warehouse. However, we occasionally ship from a combination of warehouse locations, so you may receive your order in multiple parts. If items from your order ship in separate packages, we’ll send you tracking information for each package when it becomes available.

Delivery Timelines

For the most up-to-date delivery time estimates, please refer to the shipping timeline at checkout. Delivery timelines do not include processing times. See above for details. All transit times are measured in business days which are Monday-Friday, excluding holidays.

Please note, all shipping timelines are estimates and are not guaranteed.

We are not able to ship to US territories (including Puerto Rico, U.S. Virgin Islands, Guam, Northern Mariana Islands and American Samoa) at this time.

First Pair Risk Free for 30 Days

Leakproof Underwear, Risk Free

Returns & Exchanges

Holiday Return Policy
Eligible items purchased online or in stores between November 2, 2026 and December 31, 2026 may be returned through January 29, 2027. All other purchases fall under our 30 day Returns Policy.

Standard Return Policy
New to leakproof?
Your first pair is risk free for 30 days. Wear them, wash them, and see how they work for your body. Not right for you? We'll refund the item price (original shipping excluded). Prefer a different size or style? We also offer free exchanges. Just email info@knix.com and we'll take care of you.

Purchased leakproof before? Within 30 days of delivery you can exchange for another size, style, or store credit. We're unable to provide refunds on underwear. If you ordered multiple pairs, please open, wash, and wear one pair only before initiating an exchange.

Still have questions? View our full policy here.

Rewards Members Earn 68 Points

"These are my favorite of all the period underwear styles I have tried, and I now own enough for a full cycle of wear."

- InStyle

Comfort-First Fit

Bikini silhouette with a classic mid-rise fit, medium hip and bum coverage.

Worry-Free Protection

Our newest leakproof innovation provides more absorbency without the bulk. Patented 360 LeakSeal™ technology locks in leaks at every edge.

Moderate Absorbency

Absorbs 2.5 super tampons worth of liquid—perfect for moderate flow days, light bladder leaks, and sweat. The carbon cotton gusset top layer keeps you dry.

No-Show Style

Buttery-soft and smooth fabric gives a seamless look and feel. Disappears under clothes, even leggings.

Easy to Wash

Machine washable, just like your regular underwear.

Zoom

How to Choose?

Essential

  • • Days you don’t need leak protection. Everyday freshness and moisture wicking.
  • tsp
    0 tsp

Heavy

  • • Extra peace of mind. For the first days of your cycle, light bladder leaks, or a full night's sleep without a leak.
  • tsp
    about 8-14 tsp
  • pad
    about 1.5-3 regular pads
  • tampon
    about 4-7 super tampons
  • cup
    about 1.5-3 menstrual cups

Light

  • • Daily freshness. For sweat, discharge, period spotting, or backup protection.
  • tsp
    about 1-3 tsp
  • pad
    about 1-3 pantyliners
  • tampon
    about 1-3 regular tampons
  • cup
    about 0.5 menstrual cups

Moderate

  • • For mid-cycle flow, surprise cough or sneeze leaks, or a really sweaty spin class.
  • tsp
    about 4-8 tsp
  • pad
    about 1-1.5 regular pads
  • tampon
    about 2-4 super tampons
  • cup
    about 0.5-3 menstrual cups

Ultra

  • • Ultimate peace of mind. For the heaviest period days, light bladder leaks, unexpected postpartum flow, or overnight protection.
  • tsp
    about 15-20 tsp
  • pad
    about 1.5-2.5 super pads
  • tampon
    about 7-11 super tampons
  • cup
    about 2-3 menstrual cups

Why Our Customers Love UltraThin

FRESH FIX TECHNOLOGY®

Built-in protection that feels like nothing at all.

Our patented 360 LeakSeal™ technology locks in leaks at every edge. The ultra-thin liner absorbs about 2.5 super tampons worth of liquid. 

Soft Top Layer

Gently wicks away moisture while keeping you feeling fresh and odor-free.

4.4
Rated 4.4 out of 5 stars
Based on 798 reviews
What our customers are saying
Customers say these period underwear are comfortable and provide excellent protection without the bulkiness of traditional pads. Many appreciate the thin, no-show design that works well under clothing and the stylish patterns like polka dots. Users frequently mention the confidence and peace of mind these provide during periods, workouts, and daily activities. Several note they're particularly good for teens and lighter flow days. However, common concerns include sizing inconsistencies, with many finding recent purchases run smaller than expected. Some mention the front coverage could be longer, and a few experience issues with leg holes being too tight. Despite sizing challenges, most customers praise the comfort, absorbency, and quality of the product.
85%would recommend these products
FitRated -0.2 on a scale of minus 2 to 2
ComfortRated 4.5 on a scale of 1 to 5
EffectivenessRated 4.5 on a scale of 1 to 5
Keywords
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Rating
Ratings
Height
Height
How do you use your Leakproof?
How do you use your Leakproof?
Usual Pant Size
Usual Pant Size
798 reviews
  • Rated 5 out of 5 stars
    3 minutes ago
    so sexy

    so sexy for leakproof

    LL
    L. L.
    Verified Buyer
    Reviewing
    Leakproof UltraThin™ No-Show Bikini 3-Pack
  • Rated 4 out of 5 stars
    2 hours ago
    Booktok came in amazing!

    I love the ACOTAR cross! It was really tight compared to my other Knix products but they have kept up very well.

    SC
    Sadie C.
    Verified Buyer
    Reviewing
    ACOTAR™ Leakproof Ultrathin™ No-Show Bikini Box Set
  • Rated 5 out of 5 stars
    19 hours ago
    Comfy comfy

    Very comfortable. I don't really need the period function. But I wanted the ACOTAR collections. Would purchase again if there was another collab. Rating middle ground for effectiveness because I can't tell you

    AR
    Ariana R.
    Verified Buyer
    Reviewing
    Leakproof UltraThin™ No-Show Bikini 3-Pack
  • Rated 5 out of 5 stars
    2 days ago
    Great

    Comfy and effective - so far so good.

    KK
    Kara K.
    Verified Buyer
    Reviewing
    Leakproof UltraThin™ No-Show Bikini 3-Pack
  • Rated 5 out of 5 stars
    2 days ago
    Great product

    This brand it’s amazing, the products are very comfortable, easy to wear, very effective and soft.

    NL
    Nora L.
    Verified Buyer
    Reviewing
    Leakproof UltraThin™ No-Show Bikini 3-Pack
  • Rated 5 out of 5 stars
    2 days ago
    Love!

    So cute! I love them

    MC
    Meghan C.
    Verified Buyer
    Reviewing
    Leakproof UltraThin™ No-Show Bikini 3-Pack
  • Rated 5 out of 5 stars
    2 days ago
    comfortable, no-show leakproof underwear

    This bikini type underwear is smooth and thin, and can't be detected under clothes. It is very comfortable and attractive. The leakproof panel is thin and imperceptible. Recommended for light leaks or light period days.

    RB
    Rebecca B.
    Verified Buyer
    Reviewing
    POS - Leakproof UltraThin™ No-Show Bikini 3-Pack - Last Call
  • Rated 1 out of 5 stars
    3 days ago
    Unusable after one wear

    Wanted to love these, they fit nicely and are very comfortable however the gusset discolored after one wear, looks stained, and the liner smells horrible. Followed all the care guides for washing and drying. I also have used many other period underwear brands and never had an issue like this. Attempted to contact customer service and because the pack I purchased was on clearance it was final sale and could not be returned or refunded. 75$ for one time wear.

    M
    Megan
    Verified Reviewer
    Reviewing
    POS - Leakproof UltraThin™ No-Show Bikini 3-Pack - Last Call
  • Rated 4 out of 5 stars
    3 days ago
    Love the colab

    Love the design but you need to size up. Other styles fit but this one runs small.

    SF
    Sara F.
    Verified Buyer
    Reviewing
    Leakproof UltraThin™ No-Show Bikini 3-Pack
  • Rated 5 out of 5 stars
    5 days ago
    Night court pack

    The night court pack are cute and comfortable.

    MS
    Michaela S.
    Verified Buyer
    Reviewing
    Leakproof UltraThin™ No-Show Bikini 3-Pack
  • Rated 5 out of 5 stars
    5 days ago
    Efficace

    Je recommande

    MD
    Marie-Chantal D.
    Verified Buyer
    Reviewing
    Leakproof UltraThin No-Show Bikini
  • Rated 5 out of 5 stars
    5 days ago
    I forgot I was wearing them!

    I really liked them and honestly forgot they weren’t just regular underwear!

    KC
    Kenzie C.
    Verified Buyer
    Reviewing
    Leakproof UltraThin No-Show Bikini

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