A Talon Gearbox Sprocket for Montesa Cota 123 200 240 242 247 304 307 309 310 330 models with the smaller 16mm taper fitting and for a 520 size chain.

Your original sprocket may well have had a keyway, and as far as I am aware, nobody is now making them like this. These Talon sprockets do not have a keyway, but if assembled clean and done up tight, the key is not required, it will not slip.

Available with 9, or 10 teeth.