Scrod -

I am picking up omnium cranks this weekend for my steel langster.

They seller recommended I buy a Chris king BB.

How do I measure for a BB? do they come in different lengths?

I remember on my first conversion I brought an old schwinn to my LBS and there was like 2 cm stcking out of the bb shell on either side.

Secondary question:
Is CK a good buy for a BB?

Pardon the ignorance and thanks in advance!