Exhaust Silencer: Classic styling and aerospace construction sets the Ti-4 silencer apart from the competition. The grade 2 Titanium provides great weight savings and lasting looks, while the Pro Circuit design offers huger performance traits. Fully tunable modular end caps, exclusive E-glass pillow packing, CNC-machined mounting boss, and wire meshed removable spark arrestor complete the package. The Ti-4 is a slip-on muffler that offers you the option of various head pipes. Can be used with the OEM stock or a Pro Circuit standard head pipe, offered in both titanium and stainless steel construction.