These headers have 2-1/4" diameter big tube inner runners to accommodate the highest horsepower engine.The 100% 316L stainless steel headers are completely annealed and stress relieved prior to the show quality polishing to ensure maximum durability. The header and tailpipe share a double wall design and water transfer system that even allows the option of pre-heating the incoming sea water. Even the tailpipes are exclusive to Hardin Marine, while other manufacturers continue to use a lower grade 304 quality of stainless steel for their tailpipes Hardin Marine continues to use only the best quality 316L stainless steel.More original features are the V-Tex collector design and aerospace inspired multi-axis leak proof bolted tailpipe flange, no hose type clamps or rope seals are used here. Each header offers a welded water inlet tree as standard equipment, once again you won't find any failed rubber hoses here. These headers share the latest in exhaust technology to achieve maximum horsepower gains on even the highest horsepower engines. By incorporating long staggered length runners that also provide for generous tall valve cover clearance.