RAM 1.5" Diameter Ball Mount with 2.5" Round Base (AMPs Hole Pattern) & 3.625" Square Base (VESA 75mm X 75mm Hole Pattern) The RAM-101U-2461 consists of a double socket arm, 2.5" diameter round base with the universal AMPS hole pattern and 3.625" square plate with the VESA hole pattern. The VESA plate contains a 75mm X 75mm hole pattern. Designed into the mount is a 1.5" diameter patented rubber ball and socket system with adjustment points at both socket ends of the arm. Rubber ball and socket technology allows for almost infinite adjustment and perfect viewing angles. Material: Powder Coated Marine Grade Aluminum Ball Size: 1.5" Rubber Ball Size Note: The "U" in the part number reflects product packaged in poly bag.