[Question] Why are there no 22-inch return air grilles?

Looking at return filter grilles online to replace an ancient one, and I see 8, 10, 12, 14, 16, 18, 20, 24, 25, and 30-inch dimensions.

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The hole in the (plaster) ceiling is 22x22.

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Why did they skip 22-inch sizing and jump from 20 to 24?