The RAM Mounts RAM-B-149Z-AP9U Handlebar Rail Mount with Zinc-Coated U-Bolt Base consists of a double socket arm, a diamond adapter base, and a high strength composite cradle for the Apple iPhone 4. Designed into the mount is a 1” (2.54cm) diameter rubber ball and socket system with adjustment points at the base and cradle. With a twist of the arm knob, you can move the iPhone 4 motorcycle mount to your optimum viewing position. Hardware is included in this package that can accommodate rails from 0.50 to 1.25” (1.27 to 3.18cm) in diameter. Also included are black cover caps to be placed over the exposed ends of the u-bolt and a composite adapter that can narrow the rail to a minimum width of 0.5” (1.27cm).