Silencer insert to reduce emission noise. Diameter of each end: 35 mm (~ 1 3/8 inch). Inner opening: 21 mm (~ 0.83 inch). Length: 205 mm (~ 8 inch). Suitable for various manifolds and drag pipes with a 1 1/2 inch (38.1 mm) external dimensions. Ready to install and universal use. This dB killer dampens the sound of the bike down. This avoids trouble with residents and the regulatory authorities. The typical sound is naturally preserved.