Wilwood's HD Series Fixed Mount Rotor Hats have a long standing reputation for fit, performance, and durability. HD Series hats are manufactured from premium grade aluminum alloys offering high strength, low weight, and show quality appeal. HD hats have not only been a mainstay in many of Wilwood's racing disc brake conversion kits, but they can cover a range of applications from an OE four lug axle shaft to a Grand National stock car racing hub. HD hats feature a straight bell construction with a flanged rotor mount ring. These features combine to provide maximum radial clearance between the caliper body and the hat. This can be a critical factor when trying to squeeze a large caliper inside a small wheel. Many hats offer multi-lug wheel patterns for added versatility. Some hats can be ordered blank for custom axle building and other unique applications. The HD hat configurations are divided into two groups. There are threaded hole hats for use with through-hole mount rotors, and there are through-hole mount hats for use with threaded hole rotors. When used with matching Wilwood rotor hardware, these hats provide solid mounting for a wide range of custom and competition disc brake applications. Use the ordering information link to match the rotor mount, lug pattern, offset, and the other dimensions necessary for each application.Pit Stop USA offers Wilwood HD Fixed Mount Aluminum Hat for 5/16" Through-Hole Rotors - 8 x 7.00" Rotor Bolt Circle - Undrilled Wheel Lug Pattern - 1.41" Offset - 2.78" Center Hole I.D. - .50" Face Thickness - 6.14" - 5/16"-18 Mount Hole 171-2234 at low everyday prices. Be sure to check out all of our products from Wilwood Engineering including Wilwood Engineering Rotor Hats.