2015-16 Mustang GT headers with 1-7/8" primary tubes, 3" diameter lead pipes and high flow catalytic converters designed to mate to Stainless Works exhaust. Tig welded 304 stainless steel headers with 3/8" thick flanges and 3" diameter slip fit collectors with merge spikes. This system is designed to work with Stainless Works performance connect exhausts, which maintain a full 3" diameter, and does not neck-down like the factory system. Stainless Power headers are backed by a 24-Month guarantee on material and workmanship.