Spare brass tubes for penturning project kits (8) pre-scuffed tubes per pack Each tube has a 3/8" outer diameter Cut tubes to the exact length you need for your woodturning project Use to replace damaged tubes, or to work ahead on your project Spare brass tubes for penturning project kits. (8) pre-scuffed tubes per pack. Each tube has a 3/8 Inch outer diameter. Each tube is 10 Inches long. Cut tubes to the exact length you need for your woodturning project. Use to replace damaged tubes, or to work ahead on your project.