The AV 300 Winter Shoe Cover is a deep winter shoe cover that is breathable, windproof, and water-resistant. Predominantly made of a microfiber/spandex material, this shoe cover incorporates a windproof and waterproof membrane to give protection from the elements. The elasticity of the materials allows a snug, aerodynamic fit. The rear zipper is slightly raised to prevent damage while off the bike and there is also a Velcro closure tab on the bottom that allows the cover to be opened completely, so you can pull it over your shoe before putting it on, then pull it down over the shoe. Size up, shoe covers run small.