The stretchy Castelli Pro Thermal Skully fits comfortably under your cycling helmet and it won’t bunch thanks to raw-cut edges. The thin thermal layer keeps your head and ears warm while flat-lock stitching and fleecy liner feel exceptionally soft. Start out a cold ride protecting your head and sensitive ears wearing the Pro Thermal Skully. When it gets warmer, take the Skully off and easily store it in your rear jersey pocket.