The K mounts will fit ALL modern Pentax DSLR cameras. There will be some auto functions that will not work, and will have to be done manually, but because of the excellence of some of the old glass, it is well worth it. Post this question over on the Pentax forum with the what the lens is as we have a lot of people who monitor over there that have a lot of experience with the older lenses. But we'll have to know what the lens is.