Hmm, this seems to be short on answers... I had to tiptoe through the dusty cobwebs of long-undisturbed memories to arrive at Kodak as the name of my filter set. They're 6 inches square. Each came in a yellow Kodak envelope, and within that, the thin filter material was protected by a white card-stock folder. To fit the filter drawer in the head of my Beseler 23C, I cut the folders and filters down to 5.5" square. Then cut a 5" diameter hole in the center of each folder to form a frame and glued them closed. This was in the late-1960's... they're still in fine condition, but they were used for only about 8 years.
So, there's some non-Ilford filter blather, for what it's worth!