depth gauge vs depth gage

depth gauge and depth gage both are nouns.

Word	Noun	Adjective	Verb	Adverb
depth gauge	Yes	No	No	No
depth gage	Yes	No	No	No

As nouns, depth gauge and depth gage are synonyms defined as:

depth gauge and depth gage: a gauge for measuring the depth of grooves or holes or other concavities

depth gauge (noun)	depth gage (noun)
a gauge for measuring the depth of grooves or holes or other concavities	a gauge for measuring the depth of grooves or holes or other concavities