Great for Kite projects and orther lightweight RC projects.
It seems most likely the fibres are orientated in the longitudinal axis according to the application.
This is not good for hoop stress and therefore holding pressure.
If you want carbon fibre tubing that will hold pressure, you'll need a wound tube, or rolled carbon fibre cloth.
Wound tube being made:
Carbon fibre reinforced aluminium for paintball/diving tanks/...etc:
Here is a rolled cloth tube being made (not carbon, but still a fibre composite, possibly glass fibre):
Rolled cloth carbon tube:
See how those a different to the tubes made from longitudinal fibres ?
Look they are lengthways, and don't wrap around:
You can see them splintering out.
A bit of these tubes looks like this:
The carbon fibres are very strong when pulled along their length, but if you pull from the sides, it is only the matrix holding the fibres together, and it is no where near as strong.
So consider this wisely.