RAM mount stacking modular clutch/brake base with 2 integral 1 inch diameter B size ball. Same as the B309-1 except it has two balls instead of one. For attaching to motorcyle handlebars through clutch/brake. For dimension check the RAM b309-1.pdg drawing which has the same dimensions. For use with RAM universal ball and socket mount system. Marine grade aluminum with powder coat finish and rubber ball. Lifetime Warranty.