These are the extension tubes that come with the Tube Jig, the large tube matches your tube size and the smaller one is 1/4" less. These feature plastic tube sleeve ends that use a hose clamp with our "cross bolt" glued on for tool less adjustment. The clamps allow you to fine tune tension for easy adjustment of the Tube Jig, then lock down tight when you like the tube. They also have red lines marked 1 1/2" from the end and a center line for reference. The sleeve ends are very strong until you see the red line, that is the point when they get weak. You can go beyond the line, but need to be more delicate. The tube sleeve ends are also replaceable and pretty cheap, they are super glued in the tube which is easy to remove with a flat blade screwdriver.
Destructive testing results - Can easily handle 3 foot drop with red line hidden. At red line larger, heavier tubes might break one or two of the 4 ears. Side load at red line is approximately 15 ft./lbs.