3/8" thick T6 billet aluminum wheel plate with vial and mounting holes for most 5 bolt patterns (4-1/2" - 5") and most wide 5 plus 4 bolt patterns, Anodized and laser engraved, Center hole is 3-1/4", Fits any Longacre bump steer gauge, Longacre is known for high-quality, easy to install, race proven parts designed to fit racers needs, and are built to last through harsh environments.