Call me crasy or cheap or both, but I have been cutting mast shims out of the rounded edge of Margarine containers for years. They are thinner than the real shims and wear out a little more often, but hey, there's more where they came from. You can cut about 6 out of one container. I have even cut them out of the flat side part and cut a V in the middle so it forms a cone. Works great! and I don't care how cheap you think I am.