SPUHR - R-300C
The stock adapter is optimized for medium height optical sights and is designed to work with any Mil Spec or Commercial Receiver Extension and castle nut (neither receiver extension nor castle nut are included.) Features two QD sling cups in the rear plane of the adapter.
Use of the original open sights is not possible due to the high comb height.
This stock adapter can also be used without a receiver extension if the user wants to convert his firearm into a pistol or PDW format without a stock, using only a sling.
Note: Will also work with MP5.