This is the original Magpul quick-detach (QD) sling mount for M-LOK systems.

This Magpul QD mount provides a forward attachment point for push-button QD slings, including Magpul slings. 

Features:

• Machined from mil-spec anodized aluminum
• Low profile, beveled design
• Anti-rotation design to prevent swivel from spinning
• Mounts to M-LOK hand guards and forends
• 1-1/4″ webbing
• Compatible with QD sling attachment points
• Platform: AR15, M4, M16
• Made in the USA

Resources:

M-LOK Description and FAQs
M-LOK Installation Tips