MIX

The Underdays Starter Kit

£45

Style :

Mix Brief Thong

Size :

Size guide

XS S M L XL XXL

Product fit

Low on stock. Get it while you can!

Sorry, this item is out of stock

Item is out of stock. Preorder now for shipping on

1

Preorder item

This item is currently available for preorder only.

Delivery estimate is

Free UK Delivery over £60+
Free UK Returns & Exchanges

Complete the set

Your Exclusive Invite: The Underdays Starter Kit

This one’s for you—a first-timer’s exclusive to experience Underdays. Designed for your health, comfort, and style, the kit includes 3 pairs of our everyday underwear and a sleek puffer pouch to carry your essentials. The Underdays Starter Kit is here to redefine what underwear should feel like: soft, supportive, and kind to your body. Exclusive. Limited. And exactly what you deserve.


What’s inside: Choose from a Mix Set (thong, brief & cheeky), a Thong Set, or a Brief Set. Plus, a Puffer Pouch to keep them all in one place.

Gift with Purchase: For a limited time, get a free Oil La La with every Starter Kit order. Powered by African botanics and scientific actives, this multi-benefit body oil brightens, firms, and hydrates for silky, radiant skin.

Valued at: £78 

Yours for: £45

You save: £33

  • Good for your body: Made from breathable, natural fabrics that wick away sweat, prevent irritation, and promote healthier skin.
  • Soft + supportive: Underdays underwear is twice as soft as cotton with an antimicrobial gusset for all-day freshness.
  • The perfect fit: Designed with an adjustable rise and shape-retaining stretch for ultimate comfort and flattering angles.
  • Carry your Essentials: The stylish puffer pouch makes it easy to take your new favorites anywhere—gym, work, or weekend trips.


•92% Micromodal, 8% Elastane
•Gusset: 47% Modal, 46% Cotton, 7%Spandex
•All fabrics are OEKO-TEX certified (SH015 210990 Testex)

Finally—underwear that wins 5* reviews for washing well and holding its shape. No more holes, this style was built to last.
•Cool wash, 40° max.
•Air-dry flat in a shaded area
•Do not iron or tumble dry
•Wash in garment bag

  • We offer both Next Day Delivery and Standard Delivery

Not sure?

View size guide
Select size

Your underwear deserves better

You care about your skin, your wellness, your rituals. We’re pioneering care for your most intimate parts.

Twice the softness of cotton

Our underwear is made from TENCEL™ Modal—sustainably derived from trees and twice as soft as cotton. Gentle on the skin and made to feel like nothing at all.

Let your ____ breathe freely

TENCEL™ fibers are unfavorable for bacteria growth. They wick away moisture and keep you fresh through the day. Designed to help reduce the risk of unwanted infections.

OEKO-TEX Certified

OEKO-TEX® certified —clean, non-toxic with no harmful substances

Set apart by design

High Street Brand

TENCEL™  modal antimicrobial fabric derived from trees

Synthetic fabrics

Tested by real women, with over 1,000 five-star reviews

Engineered for optimal airflow and breathability

Traps moisture

A 2cm extra-long gusset for everyday protection

Soft leg elastics designed to eliminate digging in

Harsh seams

Product details