BuyBits 1 inch (25mm) to 17mm Adapter fits Motorcycle Mounts to Garmin Nuvi SatNav Holders / Cradles Unique mount adapter which allows you to attach most Garmin Nuvi cradles/holders to motorcycle mounts using 1 inch / 25mm base Composite arm measures 1.75 inches between centres. Arm can be used with mount bases using a 1 inch (25mm) ball - adapt an existing mount. 17mm ball fits most Nuvi cradles - simply push into the (female) recess. Designed for secure dedicated cradles / holders - holder NOT included