The all new Mirrycle Road Mirror was developed exclusively to fit Shimano STI shifterbrake levers while allowing the continued comfortable use of the lever. With a minimum of included parts, the Road Mirror is ingeniously engineered to fit many different STI levers. A lot of emphasis has been placed on the design of the Mirrycle Road Mirror so it blends elegantly with today's bicycle components. To mount the mirror, pull the top of the rubber hood off the STI lever clip, slip the mirror base over the lever clip, and place the rubber hood back onto the clip we've cleverly integrated into the mirror base. When mounted on the lever, the Mirrycle Road Mirror is located in the very best position for viewing to the rear. Just a flick of your eyes allows for a quick view behind. The Mirrycle Road Mirror can be attached to either the left or right side lever. All necessary tools are included. The mirror part is a 3 diameter round glass convex mirror with a wide field of view. NOTE: The Road Mirror is not compatible with STI levers that have brake lever clips that have the open space as shown at left. The Road Mirror will NOT fit on most Shimano STI levers installed on bikes after Spring 2010. The best way to determine if the mirror will fit your brake lever is to view the Assembly Instructions link above and see if your lever has a brake lever clip similar to the one shown in the instructions.