What dimensions are needed for cyl swap?

As the title says what dimensions do you check for a cylinder swap?

using the same era ( vintage) cylinder of the gun in question, only really need the OVERALL measurement....................

Thanks Dan. I'd heard mention of the star also and wanted to be sure.

Very occasionally when using an OM cyl in a NM gun the star may need slight fitting but not if you stick with similar vintage as Dan posted.

Recognize you'll not likely find a cyl with the exact overall dimension you need. But slightly longer is OK, just file or stone the front hub gas ring to match your original cyl to fit your frame.

Ah, that's where it came from. Thanks.

http://s83.photobucket.com/user/vrieze42/media/Copyof101_0527.jpg.html