This rather rare Mamiya 645 Auto Macro Spacer extension tube is in near mint condition. This tube has only really minor signs of use with slight paint loss on the mount and slight marking from connecting lenses.
This extension tube will give you 1 to 1 (life size) magnification with a standard 80mm macro lens; a copy of the Mamiya instruction leaflet can be downloaded from the Downloads section. The instructions for the tube can be found in the 80mm macro lens booklet. It gives half life siz to life size magnification with the macro lens.