This is a Magpul Industries Stock known as the ACS-L, model MAG379-BLK.
The Magpul ACS-L (Adaptable Carbine Stock - Light) is a drop-in replacement buttstock for AR15/M4 carbines using commercial-spec sized receiver extension tubes. A streamlined version of the ACS" the ACS-L utilizes the same center storage compartment and cheek weld but removes the battery tubes for a slimmer" lighter weight package.
Features:
Replaceable 0.30 Rubber Butt-Pad;Compatible with Magpul ASAP®, ASAP® QD, and other receiver-mount sling attachments;Storage compartment in stock
