What's the difference?

[socalblue1]

The mechanics are very similar, though one will find that MiLB/MLB do not strictly follow the blue book. There are so many options and changes that each crew ends up doing things a different way. AAA has the base umpires going out on every fly ball when they are not in the infield, same as four umpire.

For HS & college umpires I would suggest the CCA book. Several states have either adopted or are reviewing these mechanics. As always, check with your assignor for what is expected.