Mamiya makes three (3) auto extension tubes for the 645 AF camera: NA401 (12mm), NA402 (24mm), NA403 (36mm).
Note:
These tubes are meter coupled but DO NOT couple with the auto focus system
Each tube provides a different degree of extension and can be used individually or together
When all three are used together, they provide maximum magnification
Using all three rings with the 80mm f2.8 lens provides maximum magnification of 1:1