The engineers at Dynomax got these units to flow much better than a stock catalytic converter by doing several trick things. First they increased the flow area over OE converters by 26%, then they made absolutely sure that it flowed extremely free, then wrapped it in a stainless steel single tube mono shell. The large body design is great for up to 455'' engines. The single tube design eliminates all the welds common with OE designs and assures leak-proof operation for greater efficiency. All this means Dynomax converters outflow OE by one third!