Zipp Vuka Alumina Clip Top Mount 31.8 22.2 Aluminum Ski 22.2 aerobar extension diameter 31.8 bar clamp diameter Does not include base bar Includes Vuka Alumina Clip Top Mount and Vuka Alumina ski-tip extensions Zipp Speed Weaponry Clip-On Aero Bars. The Vuka Alumina Clip provides a wide range of fit geometry at an affordable price.