You use this together with the blade metal grip, but you get no screws to bolt them to the blade grip, the .90 version comes with screws. You must use one 3x8 mm countersunk screw and one 3x10 mm to each arm. HK has no 3x8 mm, only 3x6, 3x10 and 3x15. I grinded down the 3x10 mm screw a little bit to 8 mm. If you dont use 8 mm, the screw blocks the bearing inside the grip.