Chris- there are several competing standards for Whole Plate film holders. The Rittreck is one distinct specimen. Then there is the Eastman standard, which is the most common, but far from universal. There is also I think a Korona standard which is different, and a Rochester Optical size, and then there are the bookform plate holders which have no standard but are made to fit the camera they were sold for at the time. Sanders- I don't think your Wista holders will fit. They MAY be able to fit with a minor modification to your back, but I don't want to say for sure because the film plane dimension may be off as well. I have two different whole-plate backs for two different cameras, but they both take the Eastman size holders. If you measure your Korona back's film-holder gate, I can measure mine and let you know if the dimensions are the same. If they're not, you may be placing a phonecall to AWB or S&S to get a set made.