UltraThin Leakproof Underwear

Many people refer to them as period underwear or period panties. But leakproof underwear covers you for all of life’s leaks, including periods (even your heaviest flows), sweat, light bladder leaks, postpartum, and discharge.

*Offer valid on select underwear and thigh saver styles on knix.com and knix.ca, while supplies last. When you purchase three or more eligible styles you’ll receive the corresponding offers:
- Buy 3+ Save 15%
- Buy 5+ Save 20%
Exclusions: Sale & Last Call items
Discount is automatically applied at checkout and is based on eligible items in your order. No rain checks or price adjustments on previous purchases.

Our Leakproof technology features a built-in absorbent liner. Depending on the style you choose, the absorbency can range from about 1-17 tsp of liquid. The result? Confident protection from sweat, discharge, periods, and light bladder leaks.

A gusset is the extra piece of fabric sewn into the crotch area of underwear.

It’s there to:
* Add comfort
* Improve fit and flexibility
* Provide breathability

For leakproof underwear, the gusset is especially important—it’s the absorbent, protective layer that helps trap and hold fluid.

Think of it as the functional core of the underwear: the part that does the real work.

Totally up to you. All of our absorbencies have been wear tested and lab tested, but some people prefer to wear one for their own comfort levels. Others have tried Leakproof Underwear throughout their cycle and know the right pair for every leak. Our advice? Do what makes you feel most confident.

We designed our products to be super easy to wash and care for. For best results, rinse with cold water first, then machine wash on a cold cycle with mild detergent. It’s that easy! Different styles have different drying instructions, so always be sure to check.

Pro tip: Don’t use softener or bleach, and never iron.

That depends on you and your flow. And remember: everyone’s flow is different.

We suggest getting used to Leakproof Underwear like you would with any other leak protection. That might mean wearing your first pair at night or while you’re hanging out at home, just so you can get a better sense of your flow and your absorbency needs.

When you’re wearing your undies throughout your cycle, you can change them on your flow and the absorbency of the pair. For example, some people on their medium flow days wear one pair of UltraThin for their work day, then switch to another pair when they get home in the early evening.

For quick reference: Styles like our SuperPlus Leakproof® Underwear are great for your heaviest flows days. Our Light Leakproof No-Show Bikini, is a great option for those days of spotting and our Super Leakproof® No-Show High Rise is a great option for heavier days.