The gt spec muffler is the ultimate in high power exhaust systems. previously available only for select gt class vehicles, we are now proud to offer the gt muffler for a wide variety of popular vehicles. the gt system is a fully polished stainless steel exhaust utilizing a massive 95mm* (3.74 inches) piping diameter channeled through a 114.3mm (4.5 inch) tip. a'pex proudly stands as one of the only manufacturers in japan to own and operate a 95mm mandrel pipe bender.