http://www.coolthings.com.au/vortex-valve-tornado-tube.html

They can be used as Tornado couplings to join bottles neck to neck when making larger rockets.

	The tubes come individually wrapped in a variety of colours.
	As standard they come with 9.5mm hole, but can be widened up to 18mm.

NOTE: They do not have a very good sealing surface inside and sometimes require to be tightened significantly in order to achieve a good seal. If these couplings are over-tightened they will crack and need to be discarded.

To seal them without over-tightening them, a pair of rubber washers can be inserted against the sealing surfaces.

They come with a 9.5mm hole, but this can be widened to 18mm for better airflow and fitting launch tubes through them.

These have been pressure tested to 270psi without breaking. See experiment: 100421_001