The only spacer the worked - Aimpoint Standard AR15 Spacer for QRP2/QRW2

I tried two other spacer advertised that they fit the Aimpoint Comp M4 but there was no way they would work.
Pros: Fits perfectly and raises the sight about 9mm just where it needed to be.
Cons: None observed

This review was written in the old system and had content requirements that are different than reviews written today.