This is a Magpul Industries Stock known as the MOE Fixed Carbine Stock, model MAG480-GRY.
The MOE Fixed Carbine Stock - Mil-Spec Model (Magpul Original Equipment) provides an inexpensive" fixed" non-collapsing stock option for mil-spec size carbine-length buffer tubes. The MOE Fixed Carbine Stock has a slim profile" improved cheek weld" and multiple sling attachment options" and is compatible with ASAP(R) Plates and PRS(R) Extended Rubber Butt-Pad. Installation is non-armorer and does not require the castle nut or lock plate to be removed. Made in U.S.A.
Features:
Fixed length for standard mil-spec sized M4 Carbine receiver extension tubes
12.2†Length of Pull
Durable polymer construction
1.25†sling loops