Castelli call it the Pioggia shoe cover, and although the name is Italian for “rain,” that doesn’t really capture the essence of this bootie. Sure, it’s completely waterproof, with sealed seams, a waterproof zipper and a silicone-sealed top edge to keep water from entering. Castelli have backed the PU-coated fabric with fleece to make this bootie warm in the coldest conditions, while the high stretch also gives it a close, comfortable and aero fit.