Equip your semi truck to be Ready for the Road Ahead™, with the Dorman 904-7904 Crankcase Breather Element that provides a safe way to vent engine gases. By utilizing a straightforward design, this replacement device is able to filter harmful gases produced in an engine before releasing them into the atmosphere. Built with rugged materials to be resistant to both heat and oil. FleetPride is your First Click in Heavy Duty®.