Fastway's new Ultra Silent Insert further reduces sound levels with a reduction range of 4 - 6 decibels*. Same great fit, finish, and easy installation as Fastway's standard silent insert. Fits all new style color anodized "cone" type Fastway spark arrestor end caps (Endos). Notes: Requires a Fastway Endos spark arrestor to install. These Will NOT fit Fastway's older style polished "snorkel" style end caps. (If your end cap is bright polished aluminum, then you have Fastway's older style end cap.) *Sound intensity level will vary depending on model, tuning, and exhaust system condition.