The new Patagonia Capilene 4 material is thin, breathable and slightly stretchy with a grid pattern of heavier insulation (think R1 with 1/2 the pile). This is a material for layer lovers. Compared to the old Capilene 4, this trades off a moderate amount of insulation for a great level of breathability. In effect, it is less effective by itself, but makes a better base layer overall.This beanie is no exception. The design and quality is excellent, but it is best used in conjunction with a helmet or insulated hood, which allows the new style Capilene 4 to shine by providing a comfortable level of heat retention and enough circulation to wick any sweat that may build up anyways.
I got this hat because it fits perfectly under my helmet. I absolutely love it for that reason. It is surprising warm on it's own but I bike in the winters and this is ideal for that purpose. It is also incredibly compact and fits in my pocket like a handkerchief.