There is a specific kind of optimism that lives in everyone who owns a 3D printer, and it sounds like this: "Yeah, that's about 5 millimeters." It is never about 5 millimeters. It is 4.6, or it is 5.4, and either way the bracket you spent three hours printing now fits like a shoe on a doorknob.
I did own a caliper before this one. It was plastic, it cost about four dollars, and its jaws had roughly the structural rigidity of a breadstick. Squeeze a little harder and the number changed. I eventually realized I wasn't using it as a measuring tool so much as a mood ring.
The actual spec sheet part
This one is stainless steel, 0-150mm (0-6 inches), and reads down to 0.01mm. It does the four measurements you actually need on a print bench: outside, inside, step and depth. It also flips between millimeters, inches and fractions with a button, which matters more than it sounds when your hardware drawer contains parts from two different hemispheres.
The feature I use most is the zero-set. Clamp the jaws onto whatever your nominal dimension is supposed to be, press zero, and from then on every reading tells you how far off you are instead of making you do subtraction in your head at midnight. There is an auto power-off so it doesn't quietly eat its battery in a drawer for six weeks, and it arrives in a hard case with foam cutouts, a spare battery and a tiny screwdriver for the battery door.
Why it's actually useful here
If you print anything that has to mate with anything else, this is the line between "designed" and "eventually worked." Checking whether your filament is genuinely 1.75mm. Measuring the wall you just printed to find out how much your slicer has been lying to you. Confirming a hole came out at 5mm before you commit a heat-set insert to it. Sizing a shaft, a bearing, a bracket, or the mystery screw you found at the bottom of a drawer.
It holds a 4.9-star rating across 609 reviews and more than 3,000 orders, and the phrases that keep repeating are exactly the ones you want on a measuring tool: accurate measurements, high value for the price, and a suspicious number of people saying "very nice caliper if you're used to the plastic ones." I felt personally addressed. Check it out here, and may your next print fit on the first try.