These Lunati Pro Blower series crankshafts are designed to withstand the extreme pressures encountered when using a roots-type supercharger, commonly referred to as a blower. They feature dual keyways, .140 in. radii on the rods and mains, a 3/4-16 in. threaded snout hole, a dual drilled flange, and 7/8 in. lightening holes in the 2, 3, and 4 rod journals. The number 1 journals are not drilled, to provide extra strength on the front of the crankshafts. The crankshafts require the use of chamfered rod and main bearings, which are sold separately.