These handlebars are drilled for internal wiring and are knurled at riser locations. Bars have a 1 1/4" (32mm) diameter and 1" (25.4mm) at the riser and handlebar control location. Bars are notched for throttle-by-wire (electronic throttle) applications and can also be used with regular cable throttle. It is strongly recommended to fit these handlebars with a one-piece upper riser clamp.