The ExpoDisc (4x5.65") lens mount_Praktica Electronic with some cosmetic wear from

with some cosmetic wear from normal use and handling

with a 28mm-ish field of view and just a happy bit of distortion

Includes wrist strap and leather case

The Mamiya 645 Pro Tele-Converter 2x N is a teleconverter for most Mamiya 645 lenses with focal lengths of 150mm or more

but a solid user

The ExpoDisc (4x5.65") lens mount_Praktica Electronic with some cosmetic wear fromThis particular Expodisc is not a disc it's a big 4x5. 65" slab designed to slip into matteboxes but it works the same as the classic. Basically, it's a specialized flat diffuser designed to facilitate setting custom white balance. Rather than hauling around a gray card, or trying to find a plain white surface, or hoping that your camera guesses correctly, you can toss this in front of your lens and lock in an accurate custom white balance in seconds.