This is set off my former Tim McAmis Ballistic Bird Pro Mod.These are cherry-3 step -2 3/8" to 2 1/2" to 2 5/8" to a set of speared 6" collectors with slight downward angle exit. Hooker supplied the materials and expert fabricator Mike Kepple built them for me. Then I sent them back to Hooker for coating.I ran them 3 seasons but not many runs. They are in perfect shape. They should work with any Pro Type chassis using the 80s/ early 90s A/R Ford Boss Hemi heads. This is a steal!