This 2.75" diameter Axle-Back system features single 4.5" round black chrome on T-304 stainless steel tips on each muffler. Using Borla(r) Stainless Steel Polish p# 21461 is NOT recommended with these black chrome tips. We suggest cleaning the tips with hot water and a microfiber cloth. A system with bright chrome on T-304 stainless steel tips is also available. Borla(r) has developed a revolutionary exhaust technology that enables our engineers to deliver unprecedented vehicle-specific control over the acoustical note of an exhaust throughout the RPM range while retaining 100% of the power-adding capabilities of Borla(r)'S patented multicore design. ATAK(r) (Acoustically-Tuned Applied Kinetics) technology produces the highest available dB (decibel) levels in the Borla(r) street-legal lineup and is designed for high-performance purists who prefer exhaust notes over their stereos. The focus of ATAK(r) is to pump the volume while retaining clarity of sound avoiding distortion typically found in louder exhausts. With ATAK(r) the sound output is tuned like a graphic equalizer to shape and focus sound waves for optimum high-volume output. The technology is based on custom-tuned attributes of the internal muffler cores which are calibrated on a vehicle-by-vehicle basis to deliver the most desirable sound. "The distance from the exhaust manifold to the rear bumper the shape of the underbody shielding the amount of ground clearance all these factors affect the sound and they're different on each vehicle. With ATAK(r) we take all this into account and the result on will blow you away all with no drone inside the cabin of the vehicle says company VP of Sales & Marketing David Borla(r)., These Axle-Back systems will blow your socks off - with no drone. Like all Borla(r) exhaust products each system is handmade in the USA by master craftspeople and features premium T-304 high-quality austenitic stainless steel construction ultra-smooth mandrel bent piping and a Million-Mile Warranty.