VERB + MICROMETER
need
noun
A device used to measure distance very precisely but within a limited range, especially depth, thickness, and diameter.
US spelling of micrometre (“one-millionth of a metre”).
noun — a metric unit of length equal to one millionth of a meter
You'll need a micrometer to measure the change in length.
A micrometer is one millionth of a meter.
i Register
In some senses, micrometer is marked as US. Watch for register when choosing this word.