Consists of a 1" diameter ball and a rubber joint. Ball mounts perpendicular to a 2" x 1.7" round base, constructed from solid marine grade aluminum with rubber coated ball joints, compatible with RAM Mount 1"/25mm mounting arms and compatible with all industry standard 1"/25mm mount compatibles Weapons. There are four pre-drilled holes in each corner of the base. Universal 1.5 x 1.188 (hole spacing) hole pattern, typically compatible with RAM mounts and other industry standard 25mm/1" dual ball sockets/arms. Features: 30 x 38mm industry standard (=AMPS) 4-hole pattern, compatible with all industry standard AMPS twists The adapter plate is used with vehicle specific mounts, motorcycle navigation, car gps navigation. Transition: 1cm=10mm=0.39inch Please allow 1-3mm error due to manual measurement. Make sure you don't mind before you bid. Due to differences between different monitors, pictures may not reflect the actual color of the item. Thank you very much! The package includes: 1 x Ball Round Mounting Base