Based in Corona, California, Pro Circuit Inc. is a leader in off-road motorcycle and ATV exhausts and aftermarket performance parts. Created by former desert racer Mitch Payton, Pro Circuit proves its products and services week-in and week-out through its tagline "We Race." Every product that dons the Pro Circuit stamp stems from the legendary Pro Circuit race team. A staple in the professional paddock, Pro Circuit Racing has earned 26 AMA championships and more than 200 race wins in more than 30 years of competition. The Pro Circuit Billet Quiet Assembly is sold as a kit which includes the quiet insert and billet end-cap. Made in the U.S.A. Note: 2007 / 2008 inserts will NOT fit older model end caps. Detailed Specifications: Quiet Tip with 4" base and 1.5" insert assembly.