XR-1® Multi-Core Racing Muffler. 3.5" Center Inlet/ 3.5" Center Outlet 6.25" Round x 14" Long Body 19.75" Overall Length. Designed for applications where a 6.25" round body can be used and will work on a wide range of vehicles. It features BORLA®'S patented Multi-Core 4 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 (CFF) 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.