Double-Ended Adapter Features a 2 Pin Side and 3 Pin Side. Easily Adjustable and Used to Rewind Brake Pistons Back Into the Caliper. Slim profile design and fully adjustable rotating body aligns the pin location for engaging into the brake caliper piston face on most domestic and import vehicles. Adapter will work on right or left hand rewind calipers. 2 Pin range is from 1/2" (12.7mm) to 1-1/2" (38mm). 3 Pin range is from 1" (25.4mm) to 1-11/16 (43mm). Use with a 3/8" square drive.