This patented quick release hub assembly was designed to quickly remove the fan for qualifying or for use in races where the fan is not needed to keep the car cool. Unique two piece design reduces rotating weight and lowers the moment of inertia which allows quicker acceleration and deceleration thus quicker lap times. Part # Description 17585 Fan Hub-Quick Release-3" 17586 Fan Hub-Quick Release-3 1/2" 17587 Fan Hub-Quick Release-4" 17588 Fan Hub-Quick Release-4 1/2" 17589 Fan Hub-Quick Release-5"