13mm Central Fork Stem Yoke Motorcycle Mount with Apple iPhone 4S Waterproof Case (sku 10419) The central fork stem yoke mount has been developed for use on motorcycles where a handlebar mounting option is not possible or desirable. 13mm fits holes 13.3mm-14.7mm (0.52"-0.58") Designed to fit sports, superbike, endurance and touring motorbikes using the cylindrical bore wall (steering head tube) of the fork stems. Light weight Aluminium. Attaches easily to the steering head tube of fork stems. First check that the stem cover can be removed leaving a central hole for the mount to fix in. Simply drop the Fork Stem Motorcycle attachment into the hole of the stem and tighten. The split shaft will expand to fit the inside wall of the fork stem. Use an Allen Key to tighten to create a tight fit. Supplied with a waterproof soft case for the iPhone 4s with a touch lens and detachable lanyard.