I have a Selmer Signet (a very decent one in fact, although they tend to be much hated), but the neck is bent. It plays very good, has a nice tone, but the angle of the mouthpiece is somewhat uncomfortable. So I've been thinking about replacing the neck. I tried to fit the neck of my B&S Chicago Jazz on my Selmer. Now that's a HUGE difference (there's at least 3 mm space on each size). Yet, there are a lot of necks sold, also online, without any size specifics.
How does one know that a neck fits a sax?