This is a Magpul Industries Magazine known as the PMAG chambered in 308 Winchester, model MAG549-BLK.
The PMAG 5 7.62 AC is a reliable and durable polymer magazine for .308 Winchester based family of cartridges and is compatible with short action AICS-spec bottom metal" to include the Bolt Action Magazine Well for the Hunter 700 Stock. Featuring GEN M3(TM) technology" a paint-pen dot matrix for visual identification" and a flared base plate for positive control and ease of retrieval" the PMAG 5 7.62 AC sets a new standard for bolt action magazines.
Features:
5RD capacity
Black polymer construction
Self-lubricating follower
Stainless steel spring
Accepts cartridge with overall length up to 2.86"