Flex-A-Lite Heavy Duty 4600 Series fan blades are 6-blade standard rotation puller fans that are designed to bring the lightweight and durability of Flex-A-Lite's heavy-duty injection molded fans to the class 5 and 6 truck markets. These fans are injection molded around a center hub made of aircraft grade aluminum using very durable and rigid fiberglass reinforced nylon making them lightweight yet retaining maximum strength!