15x1 needles is pretty much the best, the selection is the largest and are easy to find, all kinds of tips, sharp, rounded, knife edge dagger types,... Compatibility with new replacement attachment isn't as important as long as vintage parts are available. The tend to last once you have found them, there might even turn up a few with the machine. The price is not much to complain about, I would not let a five or ten dollar be any hindrance if you like the rest.