Included as standard with every Lezyne GPS Unit, the O-Ring Mount Kit comes with two sets of O-rings (options for two different diameters), a backup O-ring in each size, a rubber shim, and an X-Lock composite mounting bracket. The included rubber shim supports the X-Lock mount which is engineered to attach at any 90 angle and still allow the computer to be oriented correctly. The mount works by pressing the GPS computer in at a 45 angle and rotating it until it locks into place. Compatible with most bikes and handlebars.