sizer

From size + -er.

sizer (plural sizers)

1. An instrument or contrivance to size articles, or to determine their size by a standard, or to separate and distribute them according to size.
2. An instrument or tool for bringing anything to an exact size.
3. An object used at the airport to test to see if a carry on or personal item is the correct size allowed by the airline.
4. Alternative form of sizar (“undergraduate who received an allowance”).

• Reisz