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Here's a site for cheap US made slings Safari-Tac Multi Purpose I have one of their 2 point QA slings, that Larry Vickers used to design the BFG sling

They probably will hold up to moderate use, don't get too wound up if your rig ends up crashing into the dirt though.

PTS - "Professional training and simulation" = airsoft, made in China. Or they could be PTS knock offs even... You can get them off deal extreme Tactical Outdoor Sports Gun MS3 Sling - Black - Free...

I'd say most of the local ones are PTS