I have a 12-ga. Arrieta 570 2-bbl. set that I spec'd the #1 set of barrels to have 2 3/4" chambers and the #2 set to have 3". The barrel flats are stamped with their corresponding chamber length -- 12-70 and 12-76 respectively. The water table is stamped as you see below:



Wild Skies
Since 1951