I believe most of the recoil pads I've delt with were a large phillips head, but you'll just have to get in there with a couple different screw drivers and figure out which one fits into the screw. using an assembly type lube really helps when installing or removing pads, as it keeps the rubber from grabbing the driver, and helps get the screw out/in. Brownells sells it, but something similar, like a vynal conditioner would probably work too.