Remember the original Flex-a-lite?

well my fiberglass unit has been holding up at 7000 rpm since the mid '70s, but I have a small Moroso lower drive pulley. advertised as horsepower saving- but a dyno test on a 500hp engine=flexalite 1018 lowprofile flex fan -25hp, 418 one piece plastic -30hp, clutch fan -6hp