DetailsPRP Billet Rail Aluminum Valve Covers are made by a top manufacturer. Made with a one piece billet rail that contains steel inserts pressed in to increase longevity of the product. Sheet metal construction with custom handles for ease of removal and installation. Built in spark plug tube retainers fit a wide range of different spark plug tubes available in the market place and meet NHRA rule requirements and offer a seamless design. PRP covers also come with a spark plug wire retention system, please select wire manufacturer.