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How to Choose Period Underwear: Absorbency, Gusset and Fit
Short answer
Choose period underwear by two things: absorbency and where the absorbent layer sits. Kiri daywear holds up to 50 ml for light to moderate days; nightwear holds up to 75 ml with absorbency front to back for heavy days and sleep. Measure your waist and hips, and size down if you are between sizes.
Choosing period underwear really comes down to two things: absorbency and where the absorbent layer sits. Capacity has to match your flow, and how far back the layer reaches decides whether a pair suits daytime or sleeping. Every other detail — colour, cut, price — is built on top of those two.
How the leak protection works
A Kiri pair looks like ordinary underwear; the difference is in the gusset, where four layers are bonded together. The wicking layer pulls fluid away so the surface stays dry. An antibacterial layer neutralises the bacteria behind odour. The absorbent core locks liquid in. A leakproof shield stops it reaching your clothes. None of the fabrics contain dioxins, chlorine or rayon.
Read the millilitres, not the adjectives
Ignore "light" and "heavy" and look at the actual number:
- Daywear holds up to 50 ml — roughly 5.5 regular tampons. Designed to be worn on its own on light to moderate days; on heavier days, switch to nightwear.
- Nightwear holds up to 75 ml — roughly 8.5 tampons. The waist sits higher and the absorbent layer runs from front to back, because flow moves backwards when you lie down, so side sleeping is covered.
If your flow varies a lot across a cycle, a day-and-night bundle covers both without deciding up front.
Sizing: what to do if you're between two
Sizes run XS to L, with XL in nightwear. Nightwear is cut slightly closer than daywear, so your size can differ between the two. If you're between sizes, size down — the gusset has to sit flush to work, and a loose waistband lets it shift. Full waist and hip measurements are in the size guide.
Washing, and why it decides the lifespan
Rinse cold until the water runs clear, machine wash cold in a laundry bag, hang to dry. No bleach, no fabric softener, no dryer — heat and softener are what age the absorbent layer. Cared for this way a pair lasts years, replacing hundreds of disposables.
Where to start
One pair is usually enough to understand what pads and tampons were missing. Try a daywear pair on a lighter day at the end of your next period. Browse all period underwear, or the full range.
Prefer to see it in person?
You can see and feel our period underwear and Every Day Bras at our display inside Blomstre, Shop 401, 4/F C & D, Hopewell Mall, Wan Chai. It's open Monday to Sunday, 12pm to 9pm, with no appointment needed. Directions and details.
Keep reading
Frequently asked questions
How do I know if I need daywear or nightwear?
Daywear for light to moderate days; nightwear for heavy days and sleep. If your flow varies a lot, the Day & Night Mix Bundle gives you one of each.
What sizes does Kiri come in?
Daywear runs XS to L and nightwear XS to XL. Nightwear is cut slightly closer, so your size can differ between the two.
How long does a pair last?
Around two years with proper care: rinse cold, wash cold, hang to dry, and skip softener, bleach and the dryer.
How it works
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