Vernier caliper is indeed the correct industry word, Wyatt. Made up the "ruler-type" description off the cuff when I couldn't remember that.
Dial caliper that Bansil mentions gets no better rating from me, although hugely more accurate. Since the first time I pressed the "Hold" button on a digital where there was no way to see the readout, it's been digital calipers and no other for me since then.
Bansil hit the nail on the head; if properly trained, using properly maintained equipment, vernier calipers and height gage's can easily do serious aerospace work. The problem is that the average
person most likely has never seen a set of verniers, let alone been trained on how to read them.
As for dial calipers versus digital, it all comes down to price, as well as how well they've been maintained. I'm a CNC machinist for a living; I've still got the 12 inch Mititoyo dial calipers that I bought bought over thirty years ago that are still accurate; one of the younger guys who doesn't really seem to care about his tools has a set of Mititoyo digital calipers that are less than five years old that he's totally beat into the ground that QC is about to ban from use due to inaccuracies showing up in some of his work.
As for which set of calipers to buy from Harbor Freight, stay away from the composite one's, spend the extra ten dollars and get the better stainless steel set. I bought a set years ago when I was an on site machine repairman just so I'd have something to check bearings and seals with that wouldn't break the bank if they came up missing; while you can definitely tell that they're cheap, they're actually fairly accurate, and the part that really surprised me is how well they've held up. They're definitely more than adequate for anyone getting into the karting hobby, and won't break the bank.