Looking at various photos I'm finding I'm suffering from flue length envy.

It seems that mine is quite short, with only one extension tube which doesn't really clear the edge of the top when it's up.

Others seem to have 2 tubes - am I missing something??

Yes your are missing something......1 tube😄

Both our Troll and earlier Triton came with the standard (fixed) length of flu tubing. In addition, stowed in an accessory box containing the steadies winding handle and sink plugs etc, was a sealed plastic bag containing three extension tubes. As this was the case for both our caravans I am of the impression that a set of extension tubes consists of 3 tubes.

Agreed Deeps. My new Eriba came with zero extension tubes but I found that it needed 3 for the flue to adequately clear the canvas of the pop top.

I have two tubes, before I had two I found that the wind would buffet against the canvas and blow out the gas fire.

My existing and previous vans all had two extension tubes which are required in windy conditions

Yup - sounds like AL 'borrowed' at least one of mine which I find pretty bloody annoying.
They're only a fiver each so no real pain.
Thanks to all for the comments which also help explain my confusion about flue height with the ill fated Kampa 340

I only got one with my new Troll and ended up buying two more from AL. Three is far better but am shocked that Hymer only provide you with one tube. We had an experience early on in our ownership with only one extension when the wind changed direction and seemed to blow the fumes back through the pop top and I quickly turned the heater off. This seems a bit cavalier of Hymer and £10 saving on a £20K plus van seems ludicrous.
MikeT

Mine have arrived by return - ordered Monday and arrived Tuesday. Company Caravan Tech Services http//www.caravantech.co.uk AKV extension MR30010-20800

Re-reading the manual they specifically say 'extension' rather than 'extensions'. I suppose if you have the roof down you only need one!

Only one came with ours Colin. Be interesting to see what they say.

We have had 4 Eribas and each one came with 2 flue extension tubes.

I got my Familia 320 from Lowdhams in Huddersfield and it came with two flu extensions. When I bought my other Familia from AL in Poole it came with one....

Only had one with our PuckL and only got one with our Triton, have we been short changed

My service engineer tells me the extension is required to make the flue the correct length to prevent the heater being blown out when its windy he also added that the 2 extensions screwed together that I have would do the job............. up until then I thought it was all one piece