The heavy duty steel is designed to be more durable. The heavy duty steel is designed to be more durable Additional Features: Made of Steel Works with 4L/A|5L/B belts Idler Pulley For Mower Deck at Maya Hurley blog If you're working on power transmission systems and need a reliable V-belt pulley, this AB400-1/2 single groove sheave is built to handle the job Sheave is precision-processed through CNC to achieve high accuracy in all dimensions. There is a hub, with two screw holes on it. Standard V-Belt Pulley: For V-Belt Section A,B,5L,4L,AX,BX The pulley is formed through Welding Forming, using material that meets the American standard ASTM 1020, resulting in a product that is sturdy and durable. Pulley outside diameter:4 inch,1 Groove Pulley outside diameter:4 inch,1 Groove Inside Diameter: 1/2 inch,Standard Keyseats (1/8x1/16),Screws quantity:2,1 x Wrench Standard V-Belt Pulley: For V-Belt Section A,B,5L,4L,AX,BX Durable: 1020 steel, solid construction, Zinc-plated to prevent rust This V-Groove Drive pulley is a general Sheave for power transmission, which is applied to compressors,motors, lawn mower,snow blowers and other... Inside Diameter: 1/2 inch,Standard Keyseats(1/8x1/16),Screws quantity:2,1 x Wrench Single Groove Sheave Carbon Steel Pulley Saelno Single Groove V-Belt Pulley - 4 Inch OD, 5/8 Inch Bore For A/B 4L/5L Belts Carbon Steel Motor Pulley Lawn Mower Pulley