About Nylon|Generic nylon (polyamide). Usually refers to Nylon 6/6 or Nylon 6. See 6/6 for machining details. Good strength and wear resistance for gears, bushings, and structural plastic parts.
About Round Bar|The default starting stock for lathe work. It gets turned, bored, and parted into shafts, pins, bushings, spacers, and just about anything round.