This is the Sonic Ergo 50a aerobar. It is designed to help you cheat the wind by allowing you to get into an aerodynamic position. The simplistic clip-on design looks clean and is able to be added to most round bars. Features: Injected Venturi Armrest and ZB Bracket Forged 6061-T6 construction with Armrest made of injected Nylon and Glass Fiber Fixed extension adjustment Extension angle 44 degrees with 58mm rise Specifications: Material: Aluminum Clamp: 31.8mm (26.0mm w/ Shims)