Men's Underwear Fabrics
The Complete Guide

Modal is regenerated from beech tree pulp. Beech is a fast-growing hardwood that needs no irrigation, so modal production uses considerably less water than conventional cotton — figures of ten to twenty times less per kilogram of fibre are commonly cited.

On the body, modal's headline property is softness. It is measurably softer than cotton and it stays that way: where cotton bobbles, fades and bags out at the seat after a few dozen washes, modal holds its shape, colour and hand-feel. It is also around 50% more absorbent than cotton, and — critically — it releases that moisture rather than holding onto it.

Watch out for: heat. Modal is more dimensionally stable than cotton but it is still cellulose, and a hot wash or a hot tumble will shrink it. Thirty degrees, gentle cycle, low heat or line dry.

Read more: Modal Underwear in Hot Weather: The Science of Staying Cool. Or shop it by cut — modal briefs and modal boxers.

Micro modal is the same beechwood cellulose spun to a finer denier. Finer filament means a lighter, denser fabric with more drape and a surface closer to silk than to cloth. If you have ever picked up a pair of underwear and been surprised by how little it weighs, this is usually why.

The difference between modal and micro modal is real but subtle: micro modal feels more fluid and more luxurious, standard modal feels marginally more substantial. Neither is wrong. Micro modal is the one to reach for if softness is the single thing you care about, or if you have skin that reacts to friction at the waistband and leg openings.

Read more: Micro Modal: What Is It?

Lyocell is also made from wood pulp, but by a different route — a closed-loop solvent process that recovers and reuses more than 99% of the solvent it uses. That makes it the most environmentally defensible of the cellulosics, and it produces a fibre that is stronger, more absorbent and cooler to the touch than modal.

Worth clearing up a common confusion: lyocell is the fibre, TENCEL is a brand. TENCEL is a registered trademark of the Austrian producer Lenzing, applied to its own lyocell and modal fibres. All TENCEL Lyocell is lyocell; not all lyocell is TENCEL. The branded fibre carries specific forestry sourcing and production certification, which is what you are paying the premium for.

Lyocell's other advantage is odour. Because it draws moisture into the fibre core rather than leaving it on the surface, there is less for odour-causing bacteria to work with — testing consistently shows lower bacterial growth on lyocell than on cotton or polyester. It is the fabric to pack for travel.

Read more: Lyocell Underwear for Men: Benefits, Science & Why It Beats Cotton.

Bamboo is the third cellulosic, and the one with the most marketing noise around it. The honest position: bamboo underwear is almost always bamboo viscose, meaning the bamboo has been chemically processed into fibre much like any other regenerated cellulosic. That does not make it bad — it makes it comparable to modal rather than magically superior to it.

What bamboo genuinely delivers is a cool handle. It has a slight edge on moisture absorption and often feels marginally cooler on first contact than modal does. Where it gives ground is longevity: modal holds shape and colour better over a long life.

Read more: Bamboo Underwear for Men: The Ultimate Guide and TEAMM8 Bamboo Underwear.

Cotton is breathable in the narrow sense that air passes through it. Where it struggles is moisture. Cotton fibre absorbs up to around a quarter of its own weight in water and then holds it, so once you have sweated, the fabric stays wet against your skin and loses its ability to insulate or dry. On a still day at a desk, that is fine. In heat, on a commute, or under any exertion, it is the reason cotton underwear feels clammy long after a modal pair would have dried out.

Cotton's advantages are real too: it is cheap, it is a fully natural fibre, and plenty of people prefer its drier, less slippery hand-feel.

140s cotton is what happens when you take the fibre seriously. The "140s" refers to yarn count — a measure of fineness. Higher count means finer, longer-staple fibre, spun tighter, producing a smoother and more lustrous fabric that behaves far better than commodity cotton. It closes much of the softness gap with modal while remaining a natural fibre, which is exactly why it exists.

Read more: 140s Cotton Underwear Explained and Organic Underwear for Men.

Microfibre is finely drawn synthetic filament — typically polyamide or polyester with elastane for stretch. It does not absorb moisture the way cellulosics do; it moves it. Sweat is pushed along the filament to the fabric surface, where the large surface area lets it evaporate fast. For high-intensity training that is the right mechanism, and nothing dries quicker.

The trade-off is odour. Synthetic fibre gives bacteria a surface to colonise and does not absorb the moisture they feed on, which is why untreated polyester develops a smell that washing struggles to shift. Good performance underwear addresses this with an antibacterial finish — which is what Grade 5A treatment is for.

Read more: Grade 5A Antibacterial Underwear and STRIKE PRO Underwear: The Complete Guide.

Mesh is a construction rather than a fibre — an open knit structure that maximises airflow. Nothing breathes better, because there is physically less fabric. It is chosen as much for how it looks as for how it performs, and the two are not in conflict.

Sheer and mesh are often used interchangeably and shouldn't be: mesh has visible holes in the knit, sheer is a solid fabric knitted fine enough to see through. Mesh breathes better; sheer drapes better.

Read more: Mesh vs Sheer Underwear for Men.

Ribbed is also a construction, not a fibre — a vertical knit that adds structure, stretch and texture. Its properties depend entirely on what it is knitted from. Ribbed cotton behaves like cotton with more give; ribbed lyocell gets the structure that lyocell lacks on its own while keeping the cool, smooth handle.

Read more: Ribbed Underwear for Men: The Complete Guide.