They feature a rigid blade design, and are designed to eliminate the fan clutch.
75-2.5 bolt pattern;6 Blades;California Residents: WARNING Flex-A-Lite 19" Belt Driven Steel Silver Race Fan - 106285 These fans need less clearance compared to Flex Fans, because the blades will not flex toward the radiator. This 19 Steel Silver Race Fan is designed to eliminate the need for a fan clutch;Reduces weight;Reduces components that are not needed in racing applications;Steel blades;Premium silver finish;Standard Rotation;5/8 pilot;1.Flex-A-Lite Race Fans eliminate the need a fan clutch.