Thanks for the reply Keithwms but you've misunderstood my post. I'm looking for a 14x17 ground glass spring back, meaning the hole back that attached to the rear frame of a 14x17 view camera. Also, because standardization of film holders above 11x14 is minimal, ULF film holders were typically made to fit optimally with specific backs hence the request for a matching holder. Making a ground glass spring back is the most difficult part of view camera construction and the holders are even more difficult because of the extremely precise tolerances required assuming you want optimal results.