Twin volute design and a replaceable water pump cartridge. Perfectly balanced flow between both sides of the block. This pump uses less than 2 Horsepower at 50 GPM. The Chevy Pro Series offers 16 AN side outlets while still using stock mounting holes, allowing all or some of the water to the sides of the block and heads. The 3/4 inch shaft and 3/4 inch billet hub allow the use of a mechanical fan. Pro Series pumps are cost efficient by allowing just the cartridge to be replaced, making it no longer necessary to change the whole water pump. The cartridge can be changed out very fast, by removing the pulley and four bolts. All Pro Series water pumps use an o-ring to seal the cartridge and do not use a backing plate, so there is no gasket to leak. Whether you race circle track, road race or drag race, professional or amateur you will benefit from these water pumps.