Standard medium plastic sifter has 40 mesh screen for applying 80 mesh enamel. Plastic is approximately 1 1/4 inches in diameter.
Folks at CarEnCo consider these “small,” but if you’re looking at most places they’re listed as medium.
Most will choose 40 mesh screen, which is standard. We like to use the method of applying a layer with 150 mesh and then following it up with a coat from the 40 mesh sifter.