The ARMS #22M68 Full Spacer adds height to the ARMS #22M68 Aimpoint Throw Lever Ring(#10950). The extra elevation provides the proper sight level on flattop M-16/AR-15 rifles to enable the shooter to co-witness the iron sights. The spacer is only needed if you're not using the ARMS Swan Sleeve or the S.I.R. System on an M16/AR-15. Also works with 22TX30 TriPower reflex sight mount. *The product picture shows the spacer between the mount and ring of the #22M68 ring(#10950) sold separately. Extended length ring assembly screws are included.