WMD Guns machined aluminum Mil
Spec receiver extension tubes accept an M4-style adjustable carbine buttstock.
Six precision-machined notches on the underside provide plenty of options for
setting length-of-pull. These are perfect for a custom build or installing a
mil-spec stock on a civilian carbine, or updating a fixed-stock rifle with an
adjustable M4 stock. They are machined from a lightweight aluminum extrusion
then NiB-X coated.