"__ you kidding?" (3)

I think it could be either:

Which length description are you looking for?:

are

(Other definitions for are that I've seen before include "(We/they/you) exist" , "Exist; square measure" , "is for more than one" , "Era (anag.)" , "(They/you/we) exist" .)

I've seen this clue in the LA Times and the Newsday.

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