Everything you need to know about Flissie bamboo boxer shorts: fabric, fit, use cases, care, sustainability and shipping.
Flissie boxers are 95% Tanboocel bamboo viscose and 5% elastane. Tanboocel is made in a closed-loop process, where the chemicals used to process the fibre are recovered and reused rather than released. The result is a fabric that is soft from the first wear, breathable and temperature-regulating, dyed to OEKO-TEX Standard 100. Our honest guide to bamboo underwear covers what the fabric does and what it does not.
For warm days and thigh chafing, most customers say yes. Bamboo viscose is soft from the first wear, moves moisture rather than holding it and dries faster, so a long warm day feels less clammy. Cotton is cheaper, more forgiving in the wash, and still the fibre most medical guidance names. We compare the two properly in two years of switching from cotton to bamboo viscose.
The 6" sits mid-thigh. It is our best seller, it comes in every colour and size, and it covers the top of the inner thigh where most rubbing starts, which makes it the everyday choice under skirts, dresses and gym shorts. The 9" sits about an inch above the knee and covers the whole inner thigh, for anyone who wants more coverage. It comes in black and pine green. See both lengths.
Flissie are designed specifically for the female form. The waistband, cut, and rise are all engineered around women's anatomy, so they sit comfortably over the hip without digging, and the gusset is shaped for women. They're called "boxers" because the silhouette is boxer-style (longer leg, looser fit than briefs), not because they're borrowed from menswear.
When you're between sizes, size up. Flissie boxers are designed to fit close to the skin without compressing, and going down a size compromises the anti-chafing function because the fabric needs full contact with the thigh to glide rather than bunch. Most between-size customers report the larger size feels exactly right after one wear; the smaller size never quite stops feeling tight. The size guide has the full chart, and the size swap on your whole first order is free.
Yes. Every size from UK 8 to UK 30 is the same price. The 6" comes in every colour and every size; the 9" comes in black and pine green, also to a 30. The leg opening and waistband are graded separately for each size, so the leg still sits flat at the larger end. The full size guide is on our size guide page, and our plus size page shows live stock for UK 16 to 30.
No, and this is the single most common review comment from women who've tried other brands first. Flissie boxers are cut with a specific leg-band tension, and bamboo viscose sits close against the skin, so they stay in place through walking, running and dressing changes. If other boxers have rolled up on you before, this is the design difference you'll feel immediately. We compare leg lengths and leg bands across 10 women's boxer brands.
There is no hem ridge and no seam at the back or sides, so they sit smoothly under leggings, fitted dresses and slim trousers. Any edge can show under very thin or sheer fabric; for the smoothest finish, choose the 6" in the shade closest to your skin tone. Our guide to what actually stops visible panty lines goes further.
Many women in perimenopause and menopause wear them for exactly this. Bamboo viscose is breathable and moves moisture away from the skin rather than holding it, so you are not left lying in damp fabric after a night sweat. Some customers keep a separate set just for sleeping. We explain why in perimenopause, hot flushes and your underwear.
Many of our customers find Flissie boxers more comfortable than traditional postpartum pants in the weeks after birth. The soft, non-digging waistband can sit above or below a C-section scar without rubbing, the gusset is wide and gentle, and the longer leg stops chafing during a recovery period when movement might be limited. They're not designed as surgical garments; for those, consult your midwife or GP. Our postpartum underwear guide and C-section knickers guide go through each stage.
That is what they were designed for. The leg reaches past the point where most thighs touch, so there is a smooth layer between them instead of skin on skin: the 6" covers the top of the inner thigh, and the 9" covers the whole inner thigh if the rub reaches further down. Customers tell us about long walks, half marathons and festivals without chafing. See our chub rub shorts, or read how to stop and soothe chub rub.
Bamboo viscose is soft and breathable, there are no seams at the back or sides and no tag, and the fabric is dyed to OEKO-TEX Standard 100, which means the finished fabric is tested for harmful substances. We do not claim it is hypoallergenic or antimicrobial, because those properties cannot be shown once bamboo is made into viscose. If you have a skin condition, check with your GP or dermatologist, and try a single pair first. Our guide to fabric and sensitive skin covers what to look for.
You can wear Flissie boxers comfortably on light days or as a backup layer with a pad or period pants underneath. They aren't designed as leak-proof period underwear themselves: bamboo viscose absorbs but doesn't trap fluid the way a multi-layer period gusset does. For heavy days, pair them with period-specific products; for the rest of your cycle, they're often more comfortable than standard knickers.
Machine wash at 30°C or below with similar colours, inside out if you want to preserve the dye. Use a gentle detergent and skip fabric softener, which coats the fibres and reduces breathability. Air dry where possible; tumble drying on low is fine but shortens the life of the fabric. Avoid bleach. Looked after this way, a pair should last a couple of years of regular wear. The care guide has the full routine.
Like all dyed fabrics, deep colours such as Black, Pine Green and Plum Pink will fade slightly over many wash cycles. Washing inside out, in cool water, and air drying keeps the colour longer, and fading shows least on lighter shades such as Lavender Purple and Taupe White. If you notice colour transfer in early washes, wash separately for the first two or three cycles.
With a cool wash and air drying, a couple of years of regular wear. Bamboo viscose isn't as durable as heavyweight cotton over very long timelines, and it is fussier in the wash, so how you wash it matters more than anything else. The first thing to wear is usually the elastic in the waistband; when that goes, it's time to replace the pair.
Tanboocel is a closed-loop bamboo viscose, meaning the solvents used to break the bamboo down into fibre are captured and reused rather than released as waste, and the bamboo comes from FSC certified forests. Bamboo grows fast and regrows from the same root system without replanting. It is not zero-impact, because no fabric is, and it is still a chemically processed fibre. We set it against other fabrics in the least sustainable fabrics, and where bamboo viscose sits, and our sustainability page covers the packaging.
Flissie boxers are designed in the UK and manufactured by our partner factory which holds OEKO-TEX Standard 100 certification and meets ethical labour standards. We visit our manufacturing partners regularly. We're working toward full B-Corp certification, and our long-term goal is to bring more of the manufacturing chain closer to the UK as volumes allow. Read our story.
Wear them, wash them, and if they are not right, you have 60 days from purchase to return them for a full refund, worn or not. The size swap on your whole first order is free: please try one pair on before you open the rest, because each pair is packaged individually and we ask for the others back unopened. Return postage for refunds is at your cost. Details and the returns email are on our returns page.
