Available headers from the finest titanium offer an upgrade to a full system when used with the Akrapovi? Slip-On exhaust system. Stock heat shield or optional available Carbon heat shield can be used. Stock valve system will be removed. Let your bike stand out with more power, beautiful design, and the unique Akrapovi? sound. For 939 model, you have to use the servo motor rotation limiter (P-X170) when mounting the optional evolution header. THIS PRODUCT DOES NOT MEET EMISSION COMPLIANCE REQUIREMENTS FOR STREET OR HIGHWAY USE.