This is a brand new gearbox transmission sprocket.

Part # 41-3058 / 19T

Sprocket teeth: 19
Chain size: 520         
Chain Pitch: 5/8" X 1/4"                     

Fits: BSA B25, B44 ,B50 & C25 from 1965-73
        Triumph TR25, T25 from 1968-71