Carbon fibre. Well, it wouldn’t be a proper bit of bike kit if someone hadn’t figured out a way to get some carbon in there somewhere, would it? And Canadians Sugoi haven’t disappointed.
Their ‘Carbon base layer’ contains silver ions which they claim reduce odour, and carbon which they claim gets rid of any residual odour that the silver ions can’t vest the garment of themselves. Silver ions are already added to water for purification, and the theory is that they can provide a constant source of anti-microbial treatment for a base layer over the whole of the garment’s lifetime.
Another more common feature is a zipper. There are a number of winter base layers on the market that have a zip at the front as a way to open the layer and get a bit more ventilation. Smart an idea as it may seem, if you have more than two layers on when it’s damn near impossible to reach.
A better idea in winter is a high neck. When the weather gets really cold, most people prefer to ride with a high-necked jacket or a buff to provide a bit of extra protection to an otherwise uncovered area, and a high base layer is an extension of that. There are also more extreme examples. Rapha, for example, offer a base layer with not just a high neck, but almost total cover for your head and neck as well. It’s rather extreme, but if you really feel the cold in mid-winter or are planning on riding somewhere with a less forgiving environment than the UK, then something that provides as much cover as possible may well prove extremely valuable.