The ARP 130-0203 Upper Rocker Cover Bolt Kit is designed to secure the upper valve cover on 2004.5–2016 6.6L Duramax engines (LLY, LBZ, LMM, LML), helping maintain proper sealing and component retention in the upper valvetrain area. Built from high-strength ARP material and featuring a 12-point head design, these bolts provide consistent clamping and improved durability over factory hardware, making them a reliable upgrade for engine service, rebuilds, and high-load diesel applications.