Hi,
We have the 6", it's more the norm, I guess, but the 4" would work.... and, btw, David (Van Burgel) - my husband - says that unless you're planning on making ferrules or like good tools, you really don't NEED a Mitutoyo - grin
That said, he has one - bigger grin.
I actually own a Starrett, but mine burns through batteries faster than David's Mitutoyo, in his opinion.
Kat