... .different specifications 3.different material,good quality 4.Many types Roller & Pulley For Conveying Systems (Diameter: 89mm, 114mm, 139mm etc):1 ... type ranges:.Troughing idler. Parallel idler. Transition idler. Cushion idler Roller & Pulley for Conveying Systems (Diameter: 89mm, 114mm, 139mm etc ...