16.5's are the equivalent height of a 15" tube type tire. Ditto for 17.5's which duplicate 16's, etc. We used to use 22.5's and 20's occasionally on the same hub when changing tires on dual-wheel rear ends, etc. at the concrete plant where I ran the maintenance shop.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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