XR-1® Multi-Core Racing Muffler. 4" Center Inlet/ 4" Center Outlet 6.25" Round x 16" Long Body 21" Overall Length. Long body design works well on SUV & truck applications but can be used on a wide range of vehicles including rotary engine equipped vehicles. It features BORLA®'S patented Multi-Core 6 tube design for maximum flow, horsepower, and torque. The Multi-Core portion of XR-1® mufflers flows better than straight tubing. Recommend for high horsepower applications. Reversible design for installation flexibility. T-304 Stainless steel will never rust. Natural mill finish can be brushed or polished prior to installation. 100% welded construction for strength. High temperature T-304 stainless steel wool packing for sound control. Best of all, it's made in the USA. Just what you'd expect from the world's most experienced (and most winning) exhaust brand.