Sealskinz Waterproof Beanie
Seal Skinz Waterproof beanie hat made me look like a radioactive Smurf. Not the most flattering effect perhaps, but it's actually just what's needed for murky commutes and training runs.
Crudely, it's the same technology that goes into the brand's other waterproof, breathable kit which for the uninitiated is a three-layer system comprising a polyester fleece, Porelle waterproof/breathable membrane and knitted acrylic outer. On paper at least, this allows sweat an easy escape while keeping rain out. The membrane is crinkly, but easily ignored.