Fluorescent size-comparison pic (of the common, and some not-so-common)...
Starting on the left:
T17 (17/8's inch thickness, Mogul MiPin) GE F40T17/CW
T12 (12/8's inch thickness, Medium MiPin) Industrial F40T12/G
T10 (10/8's inch thickness, Medium MiPin) Panasonic F40EX-50(T10)
T9 (9/8's inch thickness, Medium MiPin) Lampi F20T9WW
T8 (8/8's inch thickness, Medium MiPin) Philips F32T8/Plant&Aquarium
T6 (6/8's inch thickness, Medium MiPin) (no etch)
T5 (5/8's inch thickness, Mini MiPin) ZooMed F54T5/10,000K
T4 (4/8's inch thickness, Mini MiPin) F28T4-D
T2 (2/8's inch thickness, ??) American Lighting T2-24W 3000K

That little T2 looks (and feels) so thin and fragile, especially when compared to the big old T17.....

Now there's a selection! Don't see half of those sizes in the UK!

The T17 looks mega! , I`ve heard of these, but didn`t realize they were so fat!

Well I never knew linear T9 existed! Only as circlines. That T6 is unusual too, though it was only offered as a single pin Slimine, what length is that Jay? It's the diameter of the original 28w 2D tube here
And that Panasonic T10 is a real beauty! Must be one of the best T10s I've seen so far with those caps. Looks like a nice colour too!
Still loving your whopping T17s tho! Is that one 4' I presume?

That is a superb lineup! I have never seen a linear T9 or T6 tube before. The T10 is rare enough over here but the T17 is the stuff of dreams, I don't know of anyone with a T17 in the UK.

There was someone over here in the very early 00's that had a bunch of T17PG lamps, can't remember for the life of who though and the bookmark has long gone. Was just a site with a few interesting lamps, not much technical info or anything. Think I had some of the photos saved, but that was before the Event of 2006 which lead to me losing about 80% of the contents of my hard drive. ...hence why I now backup religiously!

Thanks guys.

That T17 is indeed a beast (and for just being a fluroescent tube it has a bit of weight to it...I think its thicker glass than a "normal" one like T8 or T12)
Its actually a 5-foot tube. (this one runs on a 4-foot slimline ballast, but there also exists a 90w version that runs on switch-start(have never seen one of those in person) )
I have some of those PG17, lamps and a pic here

That Panasonic T10 is deff a nice one (and is a nice bright/clean white too), if you want I can find the 'on' pic I have & upload it
The only linear T9's I've ever seen are those Lampi's (and I have these which are labeled as T8, but they're actually more like a T9).

Yeah that T6 is rare, I didn't even know such a thing existed -- other than the single-pin slimline version.
(2 of those bi-pin T6's came randomly mixed in with a case of T8's)
I have a pic of the slimline version here
Thinking ok it now...I should do a slimline comparison pic sometime too

Interesting on the 2D, I just assumed those were T5 sized (but have never seen one up close)
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One of the guys on LG has a T11 VHO tube! I'd love to find such a thing!

Really the only 3 of these sizes I see commonly are the same as you guys... T5,8,12

Was there also a T17 powergroove in 215watts?, (F96PG17/CW), thats a hell of a wattage for a tube! , with an impressive 15300 lumens

Yep there is such thing as a 8-foot 215w powergroove I'd love to find a few of those! (I even have the proper ballast to run them just sitting around...)