Sorry it took so long to answer (2 weeks of vacation).

I haven't been able to lay hands on one (only read an article in a local newspaper & handled one for about 2 min.)

They are bigger than a 35 mm canister and open at the bottom in the middle (double wall). The "double wall" is closed at the bottom (bottom= away from balloon)

The innermost wall extends higher than the outside walls.
I think the top-ring (which clasps the balloon to the "cup") only clasps the balloon between the outer rim/wall of the "cup" and leaves the inner ring of the cup free.

look at pictures on the website in the "pimp it" section.

underneath is a cross section of the thing. I had to include it as "code" to keep the spacing more or less accurate.

If I am wrong somewhere, it's because I could only briefly handle the thing.

<pre><font class="small">code:</font><hr> ___ ____
| ------------- |
| | | | | |
| || | | || |
| | | |
| | | |
| | | |
| | | |
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| | |
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| | | |
--- ---
</pre><hr>


A whole lot of succes whit your home made version. Keep us up to date and maybe post pictures of the results?

tranx