I have an Aimpoint QRP Comp mount with spacer for AR/M4's. The Spacer is needed for Flat Top's. This mount features a positive grip thumb adjustment knob that cannot be tighten to tight because of the torque feature. This is a real Aimpoint Comp Mount. They have 2 screws on each side unlike the fakes that have three. If you need a mount for your AR this 30mm Comp mount is the best you'll find. I will trade for Glock 36 or Glock 21 13 round magazines.