Fleece Performance Billet Rocker Arm Bridges for 1998.5 2018, 24V 5.9L 6.7L Cummins Set of 12 FEATURES These bridges offer a massive 2.5 times strength improvement over the factory bridges. Machined from billet steel, the bridges are surface ground for flatness, feature improved oiling to the valve stems, and are case hardened and carburized for strength.