This patent pending hand tool simplifies the way to verify proper tappet adjustment. After adjusting the tappet, simply insert the tip of this tool under the hydraulic unit retaining clip, above the pushrod seat. In fact it is a "Go-or-no-go gauge", if the tip doesn't fit between the clip and the pushrod seat or when there is up and down end play, then the tappet is out of adjustment. Only when the tip fits nicely with no end play then the tappet is adjusted properly. Works on all OEM style hydraulic tappets in Evolution Big Twin, Evolution Sportster, Twin Cam and Milwaukee Eight. Does not work on hydraulic tappets with travel limiters installed.