This is the Magpul ASAP QD Sling Attachment Point.

Have you been looking for an easy and affordable way to add another sling attachment point to your AR-15? If so, look no further!

The Magpul ASAP QD Sling Attachment Point works with a wide array of slings, provided they are outfitted with QD sling swivels. It simply replaces your AR-15’s standard carbine stock receiver end plate and requires no additional components. 

Made right here in the USA and backed by a 100% satisfaction guarantee, what else is there to ask for?!I

Grab one for each of your AR-15s today!