S&S steel breather gears are much stronger and more durable than the factory plastic ones. With better dimensional stability at high temperatures and RPM, crankcase oil scavenging is significantly improved. Abrasive particles are less likely to get imbedded in a steel gear body than a plastic one A welded-in screen prevents particles from entering the gear cavity and damaging either the gears or oil pump Larger diameter holes means improved air flow and oil scavenging from the flywheel cavity Improved breather window timing increases flywheel cavity vacuum and crankcase oil scavenging Slotted scavenge hole increases breather pocket oil scavenging for less carry over S&S Part #: 33-4242