SPRING ACTION REDUCES VIBRATION AND NOISE TO THE ROOM ABOVE * MOUNTS TO ONE CEILING JOIST FROM BOTTOM AND SIDE FOR ROCK SOLID MOUNTING * FOR HEAVY BAGS UP TO 120 LBS - ALL MOUNTING HARDWARE INCLUDED * ALL 1/8" STEEL CONSTRUCTION - POWDER COATED TO LAST * SEE RAFTER MOUNT IN ACTION - http://www.youtube.com/watch?v=wGumclLiEkY