XR-1® Multi-Core Racing Muffler. 2.5" Center Inlet/ 2.5" Center Outlet 4" Round x 16" Long Body 21" Overall Length. Compact 4" diameter muffler body is perfect for applications with limited space and can be used on a wide range of vehicles. This muffler is sometimes referred to as a 'Hot Rod' muffler. It features BORLA®'S patented Multi-Core 3 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 continuous-filament fiber (CRF) acoustic material 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.