[QUOTE=Dr Honda;11652660]It's metric, and in the USA it's hard to find.
Not really that hard to find ... IF you know where to look.
RCFoam in Colorado Springs, CO (yup, the heart of the USA) has a huge selection of metric carbon fiber tubes. Found at:
www.rcfoam.com
So, the strongest solution is to purchase the correct diameter tubes, then put a hardwood dowel (from Lowes or Home Depot) in it at the CORRECT length. VERY strong (don't ask!) and inexpensive.
Greg