Feature revolutionary design - allows quicker Feature revolutionary design - allows quicker, easier installation without the removal of the rocker covers Material:0.4375” diameter Chromoly steel; Threaded adjuster screws into the pushrod,making installation or removal a snap Once the pushrod is installed and adjusted,the lock nut prevents the adjuster from moving.The ball ends of the pushrods are drilled so that oil can flow through the pushrod NOTE: the pushrods are designed especially for use with Evolution style hydraulic tappets. Will not work with Solid Lifters. No installation instruction packaged togetger