I don't own an inside mic either, wouldn't use one enough to make it worth while. I rough the hole in checking it with calipers then switch to telescope gauges if I don't have the right size gauge pin. If it's really critical the next step is a bore gauge. For the average hobbiests the caliper is the first step before using the mating part to get a fit. Not many here are subcontracting to NASA.
In my home shop I'm still using the first pair of Mitutoyo dial calipers I bought when I started out in 1981. I'm very confident using it to the nearest .001" of anything I need to do. I only break out the micrometers when holding tenths (.0001") is a requirement.
At night I work in a quality lab with the most sophisticated measuring equipment a large corporation can buy. We just got a brand new $163,000 roundness tester installed yesterday right next to the old one that seldom got used. There's 7 large CMM's running 24/7 too. But when someone comes into the lab with a problem most of the time it's the calipers and/or gauge pins that get reached for first.