RAM mount and double socket arm with 202 base. 2-1/2 inch diameter base with ball mount. There are 7 holes in the base; 4 holes in a standard AMPS and 3 holes 120 degrees apart. C- size 1-1/2 inch ball system. Standard-size arm length 4-5/8 inch center to center. RAM universal ball and socket mount system. Marine grade aluminum with powder coat finish and rubber ball. Lifetime Warranty.