The AN16 is for a 1 inch ID hose, and the AN12 is 3/4 inch.

 

If any body doesn't know this yet, the AN fittings are called out in 1/16 inch increments. As an example a AN16 fitting is 16/16ths hence 1 inch. I recomend the book by Carrol Smith "Nuts Bolts Fasteners and Plumbing" which is a great resource and cuts the bull as it were.

Bill Jepson