Noun
caliper for measuring small distances
Source: WordNetMicrometers are usually, but not always, in the form of calipers (opposing ends joined by a frame), which is why micrometer caliper is another common name. Source: Internet
The topmost image shows the three most common types of micrometer; the names are based on their application: * Outside micrometer (aka micrometer caliper), typically used to measure wires, spheres, shafts and blocks. Source: Internet