The Fast Feet Road Shoecover from Castelli is an aerodynamic foot covering when speed is priority number 1. It's designed for racing in cooler conditions and slices through the wind while also providing protection from the chill and decent water-resistance. The silicone-coated stretch fabric is highly elastic and smooths the airflow over the shoe's laces, straps, buckles, or dials while keeping the elements out. The ankle seam that houses the YKK zipper closure is also taped to further enhance water protection and the cuff gets a silicone bead to prevent water from sneaking in from up top. This bootie isn't insulated, so it won't do much in the dead of winter, but from 45-degrees Fahrenheit and up, it offers good protection and excellent aerodynamics.