ISC micro pulleys have a multitude of uses, but their primary function is to become a slack tender on a friction hitch. This pulley has fixed anodized aluminum cheeks, with 5/8" holes for a carabiner. The aluminum sheave is 1-1/4" in diameter and held in place by a bronze bushing. The fixed cheeks are fairly close together at the top, so you must thread a 1/2" climbing line through the side. Each pulley is individually inspected for quality and CE BSEN12278 approved.