The location and configuration of the SCAR reciprocating charging handle can sometimes be a major problem--especially if you are mounting optics with a QD lever system. Your knuckles will take a beating for sure. The GG&G SCAR Enhanced Charging Handle is angled downward so that it saves your knuckles when you charge the SCAR and clears all of the optics mounting hardware that we have tested. Will fit the SCAR models: MK16, MK17, MK20SSR, MK16S and MK17S. No more busted knuckles!