I have one FKD, it is a 13x18 cm and actually came with a second back equipped with a complete 4x5" Graflok back, including hood. The main problem with my camera is the quality of the wood used, I think it's pear wood, this is NOT dimensionally stable. The camera is held open by a large wooden sliding panel in the base, on my example this was very stiff, I persuaded it into the lock position and now use the camera as an ornament. The rigidity of the back is below the minimum I consider acceptable for a serious picture-taking instrument, and as others have said, the film holders (actually plate holders) are deeply eccentric. My camera came with 2 holders, one had plain 13x18cm sheets of glass in it, would therefore theoretically have accepted some 13x18cm sheet film, in practice trying to use the camera was just way too much effort. The sheaths of the film holders are wooden (of "roll-top-desk" type) and are also very stiff, far too stiff to pull out smoothly.