The RAM-B-149Z-347U consists of a zinc coated u-bolt base, double socket arm and square adapter base that contains the universal AMPS hole pattern. Included in this package is hardware that will accommodate rails from 1.27cm (0.50") to 3.18cm (1.25") in diameter. The base includes black cover caps to be placed over the exposed ends of the u-bolt. The included composite rail adapter can narrow the rail to a minimum width of 1.27cm (0.5") . The square adapter base contains four pre-drilled holes at each corner, making the universal 1.5 x 1.188 (hole spacing) AMPS hole pattern. he mount is designed with a RAM 2.54cm (1") diameter patented rubber ball and socket system that has adjustment points at both ends of the double socket arm; this allowing for almost infinite adjustment and perfect viewing angles.