Feature●Optimized Performance: 1:1 pulley ratio ensures effective cooling without sacrificing power, ideal for engines operating below 7000 RPM.●High-Quality Construction: CNC machined aluminum with deep grooves prevents belt slipping and enhances durability.●Versatile Compatibility: Perfect for 602 and 604 crate engines, with double groove pulleys facilitating use of additional accessories.●Comprehensive Package: Comes with a matched pair of heavy-duty belts, eliminating the hassle of finding the right length.●Installation Note: Thicker than stock pulleys; longer 3/8" bolts needed for installation (purchased separately). Check compatibility with specific water pump models.Description Not applicable to water pump # 910-15590 due to interference with cast ribs on water pump. Note: The lower crank pulleys in our combo kits are manufactured thicker than normal stock pulleys. This requires longer 3/8" bolts to be purchased separately. Allen head type bolts recommended. Get the correct pulleys for your application by learning which water pump you have as explained in our tech article. SBC - Short vs Long Water Pump.