StopTech stainless steel brake lines are a great upgrade for your BMW. The stock rubber brake lines flex, slowing down response, and performance. StopTech stainless steel brake lines do not flex, and will provide a quicker, and more firm pedal response. StopTech uses a Teflon inner line that resists pressure, and will not degrade due to exposure to brake fluid. StopTech stainless steel lines also feature a clear abrasion resistant cover for protection against chaffing. StopTech stainless steel brake lines for the 135/335 are sold as a pair for the front and a pair for the rear.