High Performance Cam Follower/Tappet. Oversize Diameter, Standard Thickness. O.D. = 1.395" (.020" larger than standard); Height: .837" (standard size); thickness = .224" (standard). High Performance Tappetts. XKs Unlimited now manufactures its own line of light weight cam followers. Available in two sizes and applications: Over-size diameter and standard thickness; and over-size diameter with extra-thick top. The over-size diameters allow for a clean-up bore of worn cam follower guides. The extra-thick tops should be used when running heavily modified re-ground cams. This allows use of the standard shim range rather than extra thick shims which have a tendency to move out of place.