I cannot get a 2" stir bar to be stable on my stir plate at any speed in my 1L Erlenmeyer flask, only 1" will work. The opposite is true when I use a 2qt mason jar, go figure.
I got a big container of various sized stir bars on ebay (probably 20 bars total) for like $20 which isn't that much more than homebrew stores want to charge for a single one.