For mounting on the Ahead stem 1 1/8", below the existing head set cap. With a twist, the Com/Smartbag can be mounted vertically or horizontally thanks to the oversized bayonet mount. The lower extra compartment with rubberized Velcro straps not only offers additional space for keys and money but also for the +Com/Unit power bank for inductive charging. Splash and rain protection cover. Maximum smartphone size 155x80x15 mm.