I didn't know K&S even sold metric tubing until I asked them to add it to their product line. When I found out they did sell tubing in metric sizes I ordered some right away. The pieces arrived unharmed and were exactly as advertised, 3 mm OD with 0.45 mm wall. That gives a 2.1 mm ID which is perfect for working with 2 mm solid rod like SS shaft material. Not too tight, not too loose, just right. Thanks K&S!!!