The stained glass cutter is one of the most important tools you will buy. A good stained glass cutter will make you a "good cutter". There are inexpensive cutters you can get for a few dollars, but they have a steel cutting wheel and won't last very long. In addition, their handle is usually not very comfortable. A good stained glass cutter will have a carbide cutting wheel and either a long straight handle or a pistol grip handle. Either one works well and will last you a long time.
