higher capacity than the standard pump and better quality uses a cast impeller as opposed to some aftermarket pumps that only have a pressed steel one. these higher quality pumps have a much larger impeller than the standard pump which sticks into the block more. it moves more coolant and reduces cavitation.
will fit all 1275 and small bore 998 - 1098 engines. the 850 and 997 engines will need a small amount of metal removing from the inner face. the test is to fit the pump loosly without a gasket to make sure there is clearance.