These Metal Mask Inserts (Bidia) are for printing from 35mm Mounted Slides in the Durst Bimaneg Negative Carrier, which fits the Durst M805 and AC800 Enlargers.
The Durst Bimaneg Negative Carrier is made of die-cast aluminum, and features adjustable masking strips, register pins, and automatic centering.
With the aid of these mask inserts and glass plates, the Bimaneg Carrier can be used for enlarging film formats up to 6 x 9".