Oil Pump Worm Gear replacement part compatible with chainsaw models 017, 018, 019, 021, 023, 025, MS170, MS171, MS180, MS181, MS190, MS191, MS210, MS211, MS230, MS250.This gear is designed to transfer power within the oil pump system to proper lubrication during.Constructed to match specifications for fit and function.Install using standard tools and follow standard procedures for chainsaw maintenance.