The T15 torx fasteners on the accessory mounts and included rail sections. I barely tightened one and it deformed the inside of the keymod slot. Rail was oriented correctly. The shoe on the backside of the rail left a small gouge/dent on the bevel on the backside of the slot at flaked the finish off. Was not torquing the crap out of the screw. Not concerned about the finish, just wanna make sure I am installing them correctly.