High Performance Tappetts. XKs Unlimited now manufactures its own line of light weight cam followers. Available in three sizes and applications: Standard diameter and thickness; 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.