Snap Link, or Carabiner, 5/16" diameter
The 3 1/8" long snap link is 5/16" in diameter It's rating is 350 lbs. Also known as a spring-link. Electro-polished steel. It can be used for a sturdier connection for fastening feed bags inside the trailer. It will fit into all the grommets on our trailer feed bags. We like it because it has no sharp edges that the horse can catch himself or his blanket on.
Wikipedia: A carabiner is a metal loop with a spring-loaded gate used to quickly and reversibly connect components, most notably in safety-critical systems.
The 5/16" snap link is NOT rated high enough to use with safety chains on trailers!