Optiline Opti U-Type Pro Titan Heavy Duty Handlebar Mount Handlebar mount that fits all handlebars with a 22 to 28mm diameter. This mount is compatible with all Optiline cases and uses the Duo Lock Quick Fixing/Release system. The Titan is made of metal which makes it heavy duty. - Optiline Opti U-Type Pro Titan Heavy Duty Handlebar Mount Size