The RAM 4" rubber suction base mount consists of the 1" dia. ball and socket system with RAM Plastic Cradle for the Garmin eTrex Color Series. The rubber suction cup base has a 1.0" diameter rubber ball connected at right angles. The suction cup is designed to hold on any smooth non-porous surface, but for best result, mount the suction cup on a glass surface. The ""U"" in the part number reflects product packaged in poly bag. For additional specifications, see components and drawings tabs.Powder Coated Marine Grade Aluminum1 Inch Rubber BallBlack Powder Coat