This was designed to allow the user to take 250 exposures before having to reload. It was for use with the PMD or W-6 drives and was intended for use by sports photographers, laboratories and surveillance systems.

There seems to have been some collusion with Olympus in the manufacture of the back as Olympus 250 exposure film magazines can be used instead of the more hard-to-find Contax ones.

Removing the back from an RTS/RTSII or Yashica FR, it was necessary to add the PMD/W-6 unit to the camera base and then slide the camera and motor behind the roller on the front of the 250 back and then push the heavy locking unit on the opposite side to clamp the camera and drive in place. The 250 back had to be used with the PMD/W-6 because the rear of the unit blocked the lever-wind. The battery unit for the drive could be attached to the base of the 250 Back if desired.

The Back could be used to fire the shutter via the 3-way lockable button on the front. The front also offered tripod bushes on each side of the unit, each hidden behind a knurled knob.

Contax also produced a 250 Film Loader for the back - the Olympus loader was also equally applicable - that ensured correct loading of the film magazines.

In use in laboratories or surveillance systems, the drive and bulk-back combination was often powered by the PMD AC Control Box, even though its frame counter was limited to a maximum of 99, as it could set intervals from 1 second to 24 hours.