The Ulter Sport Performance Exhaust range includes BMW fitments for 1 Series, 3 Series, 5 Series, 6 Series, X6, Z3 and Z4 models. Ulter performance back boxes we supply are designed to produce performance gains and offer good looks from stylish tailpipe designs. Manufactured using aluminised steel or in the Premium range Stainless Steel the silencer box is has closed chambers. This is to increase the effectiveness of the sound absorbsion material and is less restrictive than the standard o/e exhaust. A by-product of the design is a sports exhaust sound which is deeper and louder than standard. Ulter exhausts are designed to use the cars original mount points where possible. Ulter back boxes in most cases cost a similar amount of money as main dealer standard o/e replacement item so are a cost effective option considering the benefits.