Fine fiberglass and highly heat-resistant resins make this silencer a superior choice for reducing noise on your ski boat. The lightweight silencer is neither affected by nor a conductor of electrolysis or any other type of electrically induced corrosion. Resistant to rust and deterioration from fresh and saltwater in either gas or diesel systems. Will not exceed manufacturer's maximum back pressure limits or decrease performance. Easy to install. 12L. Sold individually. 4 Ultimate Ski Boat Bullet Silencer each