I have a 1957 BSA Imperial Featherweight. The rifle has the ring and bridge cut with a 19mm dovetail to take a proprietary Parker-Hale ring set. It's a simple dovetail (not double like a Weaver or Picatinny) with a vertical pin in the bridge to take recoil. After three months of searching I was unable to find a set of the correct Parker-Hale rings for my rifle and scope, but I did find a message someone left about being able to use some Warne rings. So I called Warne a while ago and talked to one of their techs, who knew all about the BSA and what rings fit. Unfortunately I forgot to write his name down while I was scribbling notes... They sell a kit with two CZ550 front rings to fit the BSA. He said some BSAs don't have the dovetails on the ring cut all the way to the front; for those, the end of the dovetail acts as the recoil stop. Some BSAs have a square hole on the side of the bridge which interferes with ring fitment. My rifle doesn't have the square hole, which is good, but the ring dovetails are cut full length, so I'll have to drill the rear ring to take a recoil pin like the Parker-Hale rings. Warne makes that particular CZ ring in 1" or 30mm, and in "medium" (.425" high) and "high" (.535" high). They measure the height from the dovetail to the bottom of the ring, so add .50" or .59" to the centerline of the scope tube. They don't make a short ring for this application. The tech said Warne doesn't have a part number for the two-front-CZ-ring kit, so you can't order through their usual distributor network. But they'll sell you the correct rings for $58, presumably plus shipping. tl;dr: the rings will clamp onto the CZ dovetail, but if your rifle has full-length dovetails you'll have to drill the back one to take a recoil pin.