Fits 1989 to 2002 12 Valve and 24 Valve 5.9L Cummins engines. 24 Valve engines have to be converted to a p-pump to use this cover. Will not fit VP44 equipped engine, but we now have one that will fit VP44 equipped engines. Just redesigned in early 2018 with even more roller rocker clearance for the link bar lifters that some of the engine builders are currently using. Billet side cover includes o-ring to seal against block and stainless hardware. Starts out as 3/4? thick material then fully CNC machined in house. Will not fit common rail engines. Now comes with baffling built in. Breather ports use -12AN male o-ring boss fittings. This fits all of the roller lifters that we know are being used, however because we may not be aware of every possible combination someone could come up with for roller lifters the customer needs to verify clearance on his engine, as is the case with any part that is installed on any engine.