These special wooden-handled steel reamers are designed to properly taper the holes for bridge pins. They're semi-fluted, to help keep the holes round. This 5-degree reamer tapers from approximately .350" to .135". It works for vintage-style pins, as well as modern Martin and Collings bridge pins. (Slightly) cheaper versions can be found, but these are the best way to ensure accurate fitting. Please note that handle wood and colour may vary.