GT Series hats are precision machined from premium aluminum alloys for high strength and attention to minimized weight. Hats in this category 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. Straight Bell Hats are most often used with 11.75" to 13.00" diameter rotors with 6.75" or 7.00" rotor mount bolt circle rotors on stock car front hubs and rear axles.