Description The RAM-B-347U base consists of a 1″ diameter rubber ball connected at right angles to a 2″ x 1.7″ square base. The base has four pre-drilled holes at each corner, making the universal 1.5 x 1.188 (hole spacing) AMPS hole pattern. This adapter/base is designed to hold the following devices: Garmin® zumo™ 400 Garmin® zumo™ 450 Garmin® zumo™ 500 Garmin® zumo™ 550 Garmin® zumo™ 660 TomTom Rider 2 TomTom Urban Rider Material: Powder Coated Marine Grade Aluminum Ball Size: 1″ Rubber Ball “B” Size Note: The “U” in the part number reflects product packaged in poly bag