Good question, Debbie! Jewelers' saw blades come in a variety of thickness from very fine through very coarse (8/0 to 6). The size (#) of a blade describes how many teeth there are per inch; the more teeth there are the finer the blade is. Of course, the wider the blade is, the more kerf (the part of the material that is lost when cutting). For cutting 20-gauge wire, you can use blade size 2/0 through a 1. Most folks (including me) like a size 1/0. Just be sure to keep the blade lubricated by using a product such as beeswax.