Yes there is a tool can use but if you dont have it you can use a pair of needle nose plies if it has four notches in the piston or a large flate blade screw driver if it has a cross in the piston. Just spray the piston boot with wd-40 and turn the piston in clockwise until it looks flush with the caliper make sure that one of the four notches or the end of the cross is facing straight up and down so that the brake pad can be installed correctly. The caliper piston is spring loaded as the brake pad wears the piston turns out counter clock wise.