|Abbreviated mm, no period.
In text, usually spelled out as a noun or adjective, although may be abbreviated as an adjective in some
a caterpillar 25 millimeters long
a ten-millimeter-wide line
but 16-mm film
In photographic data, film and lens sizes are often written without a
Either style is accepted as long as it is
See also kilometer, km, meter, m, centimeter, cm, METRIC AND INTERNATIONAL MEASUREMENT.