Levers go on ejection port side. Right handed shooter will not have lever snag on web gear when gun is laid across chest. We prefer to keep them on the right side .There is no right or wrong on this to be honest. They have been done both ways in the military. With the mount you have the optic will be on center either way you have that spacer. The Aimpoint spacer was not made symmetrical so it looks kind of weird.