Seamless Bikini

Regular price £21.95
Tax included. Shipping calculated at checkout.

These seamless period pants are ultra-thin, super smooth and truly invisible. Bye-bye pantyliners! Designed with soft, lightweight nylon, they are super stretchy, comfortable and can be worn seamlessly under anything.

The breathable fabric keeps things nice and cool, and of course, our signature built-in tech absorbs moisture and prevents leaks, holding up to 2 tampons' worth of blood for up to 8 hours, keeping you oh-so-fresh. 🌸

  • For Periods, Leaks and Incontinence
  • Holds Two Tampons' Worth / 10-15ml
  • Wear For Up To 8 Hours Leak-Free
  • Soft, Stretchy and Comfortable
  • Lightweight and Quick-drying
  • OEKO-Tex Certified Materials
  • Free From Toxins, Chemicals and PFAS/PFOA

Materials: Body95% Nylon 5% Elastane Gusset: 100% Cotton, Breathable PUL Packaging: 100% Recycled and Recyclable Cardboard

🍃 Bleed Green: Each pair of our period pants replace 200+ disposables from going to landfill, reducing your waste by 99.5%

🤝 Giving Back: For every purchase, we give back to someone in need. Find out more about our #ByYouForThem giving back scheme here


We offer free shipping on all UK orders and free shipping on International orders over £75.
For same-day dispatch and next day delivery, please place your order before 1pm.
All orders are dispatched from our UK warehouse using trusted couriers such as Royal Mail, DHL and DPD. 
Think our period pants sound too good to be true? Take them on a risk-free trial for 60 days!

If our undies don't work as promised, let us know within 60 days and we'll refund you, no questions asked. The 60-day risk free trial applies to one worn pair of undies only. Refunds will be paid to the original payment method that was used to place the order.
🚿 Rinse after use.
🧽 Machine wash on 30-40 degrees.
 🍃 Hang to dry or dry indoors on a radiator.
⚠️ Do not use fabric softener or bleach. No tumble drying.
And that's it! Your FLUX Undies are ready to wear again!

Our Period Pants Are:

Sustainably Manufactured

We only use eco-friendly materials that are sustainably manufactured

Vegan and Cruelty-Free

Made from natural materials and never with animal materials or testing

Free From Nasties

Certified safe for skin and free from toxins, chemicals and fragrances.

60-Day Money Back Guarantee
How They Work

Our period pants absorb up to 5 tampons' worth of liquid, yet they look and feel just like regular undies.

Our built-in tech works like this:

1. Top layer wicks moisture away from the surface quickly, to keep you dry

2. Our middle layers absorb your blood and lock in your flow

3. The bottom layer pushes liquid back up and keeps you leak-free

It's simple. Just wear, wash and reuse.

Blood, Sweat, Whatever.

Three layers of fabric absorbing liquid showing how period pants work

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Customer Reviews

Based on 10 reviews
Anon (Stamford Hill, GB)
Flow: Moderate, Light
Products used: FLUX Undies, obvs!, Menstrual cup
So far, so good

Does what it says on the tin. Have used these for 2 periods now, I either use them with my menstrual cup on heavier days just in case, or on the last day of my period.
They're quite thin, which is great, and the design isn't bad either.

R.Z. (Brescia, IT)
Flow: Light
Products used: Menstrual cup
Seamless Bikini

I tried "Seamless Bikini". I really love the seamless style, because I use to dress a seamless pants.
I decided to buy this period pants, to have more protection with the Menstrual cup and stop to use panty saver during my periods. I used it at the beginning and the last daies of my periods when is not good to use the menstrual cup.
This is an amazing combo: confortable and eclogical. I'm feel free and quite!

Eve Mcnaghten (York, GB)
Flow: Moderate
Products used: FLUX Undies, obvs!, Cloth pads
Super comfortable & absorbent!

I absolutely love these flux period undies! They are so comfortable, super absorbent and leak proof, they are so discreet too! it feels like I’m free bleeding! I love them! I need more!

Georgia (Diss, GB)
Flow: Heavy
Products used: FLUX Undies, obvs!, Disposable pads
Game changer

I ordered these in a size L and they fit perfectly, as well as being lovely and discreet. I bought these ones with the intention of using them at the very end of my period when my flow isn’t heavy enough to use a pad and they have changed EVERYTHING! pads are really irritating on my skin, especially towards the end of my cycle for some reason, so these give me alllll the comfort! I was worried i’d feel gross using these (been using pads all my life) and they literally just feel like normal pants - no lingering blood or feeling that horrid leaking sensation in ya pants!! V impressed!

Amy Ross (Northampton, GB)
Flow: Moderate, Light
Products used: FLUX Undies, obvs!, Tampons
Comfortable & discreet

Bought these to test out before investing further. Really pleased as they're really comfortable, aren't bulky at all, just like normal underwear. I will definitely be investing in more of these over time in a bid to reduce plastic waste (traditional tampons) each month.

Andrea (New Cross, GB)
Flow: Heavy
Products used: Menstrual cup
Good, thin but sizing completely off

Looks great and without too padded feel. Although size S looks like M or L comparing to small high waist I received that seemed like xs or xxs. Therefore it was loose and orone to leak