This oil pump worm gear is designed to fit specified chainsaw models including 017, 018, 019, 021, 023, 025, MS170, MS171, MS180, MS181, MS190, MS191, MS210, MS211, MS230, and MS250.It operates within the oil pump system to consistent lubrication during use.The gear is engineered for compatibility with the listed chainsaw series and functions as a replacement part for worn or damaged components.It is constructed to maintain proper alignment with the oil pump mechanism.