The RAM-B-202-G4U consists of a 1″ diameter rubber ball connected to a flat 2.5″ diameter base. This mount has pre-drilled holes, including the universal AMPS hole pattern. Included are 3x (#8-32 x 5/8? PH PD Mach Screws) and 3x (#8-32 SS Nylock Nuts) that will connect the RAM-202-G4U to the bottom of the Garmin echo?. Compatible Devices: Garmin echo? 100 Garmin echo? 150 Garmin echo? 300c Material: Powder Coated Marine Grade Aluminum Ball Size: 1″ Rubber Ball “B” Size