Two inches of range would be perfect for sizing bits, fasteners, bolts, screws, etc. I tried carrying a messograf pen for a while but they're wildly overbuilt a

Two inches of range would be perfect for sizing bits, fasteners, bolts, screws, etc. I tried carrying a messograf pen for a while but they're wildly overbuilt and heavy. Amazon, eBay etc sell a caliper keychain but the tolerances are too loose for it to be useful and it has no vernier scale.