I bought one and installed in my 77 Chinook. Mine was 1.25 long. The ones I can get are a perfect fit. turn to right back to center to lock and remove key. turn to left back to center to unlock. Sure easy. To remove your old core, you will need to take out 3 screws on back cover. see photo.. These are seriously hard to find.. You need to pull out the one you have to make sure it is the 1.25 inch length. if you have the short one contact me directly. I think i can get them.. Old stock and may be able to get a few more..