4 in round swivel fixture hangers with 1/2 or 3/4 in pipe and dedicated ground wire for round/octagon boxes and rings are used to hang industrial lighting fixtures, security cameras, motion detectors, occupancy sensors and other electrical/electronic devices from overhead ceiling installations. The are great in industrial settings where the pipe stem or fixture might be subjected to motion or vibration. Their dedicated ground wire connects swivel-ball knuckle and steel cover, so the two permanently bonded to ensure a proper ground.