Careful here chaps. The crank in an MC18 is completely different to the later 21 and 28 models, and is not interchangeable.

The centre bearing is different in that it doesn't run a combined bearing/seal like the 21/28 crank. It's a plain open bearing. There's then a seperate seal that runs alongside this bearing.

With this in mind it would probably be a cheaper replacement part compared to the 21/28 crank centre bearing. If you can find it of course.