This is a Allen Sling known as the Solo, model 8910.
The Solo Single Point Sling is an adjustable" heavy-duty 1.5" web construction shoulder strap with metal scissor type attachment hook. The sling also features a shock absorbing bungee covered in heavy-duty web material. The sling is designed to clip to the receiver or upper stock of a tactical rifle. Adjusts from 42" to 54".
Features:
Adjustable heavy-duty sling;Features shock absorbing bungee