Notched necks for easy clamp - on installation. Reversible design for installation flexibility. High - quality T - 304 austenitic stainless steel will never rust. 100 welded construction for strength. Free Flow design for improved performance. High - temperature continuous - filament fiber (CFF) acoustic material for sound control. Natural mill finish can be brushed or polished prior to installation. Best of all, it's made in the USA and backed by Borla's Million - Mile warranty. Just what you'd expect from the world's most experienced (and most winning) exhaust brand.