I have a lot of balsa wood strips that I use with my model railroading projects. I use the strips, which are about 9/16" wide and square for pipe filters! I cut them down with a sharp knife to about 1 3/8" long(same as the filters), and then scrape them lengthwise until they fit the pipe. This works for me when I want to use a filter. They are inexpensive and can be found at Walmart or Hobby Lobby! Or, you can just smoke the pipe without a filter!