When you hung the Lighting or speaker on the truss,You must use the appropriate clamp hook, You must select the appropriate loading capacity according to the weight of the lighting or speakers, and the diameter of the hook aperture as near the truss's diameter,So the moving head light won't shake when it running The hook can Prevent the lighting or speaker fell to the ground, Result in equipment damage,or Avoid hurting people under the equipment Pipe diameter:29-35mm Load bearing:50kg can use for moving beam,moving spot...big and Weight is heavy goods