RR 50T Spur with Castle 13T Mod-1 Pinion - Not a chance

RR 50T Spur with Traxxas 13T Pinion - Sloppy, though it does fit. Rolling the pinion on the spur is not totally smooth.

RR 50T Spur with RR 11T Pinion - Match made in heaven! The pinion and spur mesh deeply and turn smoothly.

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