One (1) lower arm for 4-spring tarping system; made of lightweight, ultra-strong aluminum. Arm measures 78" long and 2 3/4" wide, expanding to 3 1/2" at pivot end. Brace measures 1/4" thick and is welded to either side of the arm, with two 1 5/16" holes to accommodate pivot pin and springs. Works on both driver and passenger side.