Wilwood disc mounting bells (hats) are precision machined from premium aluminum alloys for high strength and attention to minimized weight. They feature threaded rotor mount holes for use with standard through-hole mount rotors. Threaded hole hats may also be used with T-Nuts or bobbins designed for use with specially machined slotted hole dynamic mount rotors. When used in conjunction with matched Wilwood rotor hardware kits, GT hats provide solid, reliable performance in the most demanding conditions.