This is a Q.D. Sling Swivel Pocket (Port) that will thread into any hole with 10/32 threads to allow the use of a Q.D sling swivel. Machined of steel with a black oxide finish. Windham Weaponry uses this part on our 300 Blackout Rifle with the Diamondhead VRS-T handguard. Made in the USA. This part will also install on our VEX tubular free float handguard (as shown in separate photo).