Chamberlain Sears LiftMaster Garage Door Opener Shaft & Sprocket Part  41A4252-7G 41A4252-6G
41A5021  , 41A5021-I , 41A5021-1 , 41A5021-2  ,  41A5021-3  , 41A5021-3D , 41A5021-3E
41A5021-1M-315
only chain drive units