Stainless Headers Mfg.&nbsp; 3.5&rdquo; to 4&rdquo; Stainless Exhaust Header Transition Muffler Adaptor - American Made Manufactured By Stainless Headers Mfg., Inc. in their U.S. Facility These transitions work great for joining exhaust  header - turbo down pipes Fabricated from an American made .065/16 gauge 304 stainless steel Sized from 3 1/2 OD and transitions up to 4 OD final size 4 Overall length