The replacement chain sprocket is also known as the Drive Sprocket is part of the Clutch Drum for the Stihl chainsaws listed below.
FITS CHAINSAW MODELS
021, 023, 023 L, MS 171, MS 181, MS 181 C-BE, MS 210, MS 210 C-B, MS 210 C-BE, MS 211, MS 211 C-BE, MS 230, MS 230 C-B, MS 230 C-BE, MS 250, MS 250 C-B, MS 250 C-BE