RAM 2 x 1.7 Base with AMPs and 1 Ball for the Garmin zumo｣ｬ TomTom Rider & Urban Rider 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｣ｬ 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 RiderMaterial: Powder Coated Marine Grade Aluminum Ball Size: 1 Rubber Ball B Size