This is a Daniel Defense , model 03-021-30029.
The Daniel Defense Rail Mount QD Swivel Attachment Point is designed to allow the operator to mount the popular Heavy Duty Push Button Quick Detach Sling Swivel. This mount allows the operator to mount the swivel anywhere along their rail system. The Daniel Defense Rail Mount QD Swivel Attachment Point has been designed to limit the rotation of the swivel to prevent the operators sling from becoming tangled. The Rail Mount QD Swivel Attachment utilizes Daniel Defense's patented "Rock and Lock" one piece mounting system for a more robust and streamlined attachment point as well as simplified installation on any MIL-STD-1913 picatinny rail. This mount includes a Heavy Duty Push Button Quick Detach (QD) Sling Swivel which accepts sling straps up to 1.25".
Features:
6061-T6 Aluminum
Military Specification Hard Coat Type III Anodized
Durable 1.25 Loop