dynomax ultraflo. they are very similar to magnaflow, preforated core with packing. they just use different types of packing. both welded construction. i know maganflow offers stainless the one i had was not stainless. in fact it rotted out and the end blew out on my truck in 2 years of daily driver use. id still buy another. oh yeah the warranty dont mean crap if you dont register it. lol.