Which tool provides the most precise measurement of small dimensions, like the diameter of a bolt?

A CALIPER (vernier, dial, or digital) provides PRECISE measurement of small dimensions — including outside dimensions (like a bolt's diameter), inside dimensions, and depth — often to thousandths of an inch or hundredths of a millimeter. ASVAB Shop Information tests measuring tools. A TAPE MEASURE or YARDSTICK is for larger, less precise measurements. A MICROMETER is even more precise for very small measurements. Calipers are essential for machining and precision work. Knowing the caliper measures small dimensions precisely is commonly tested.