Tube coolers?

Are there good sleeve-type tube cooler things if I have my tubes on a shelf with not too much top clearance above the tubes? Thanks in advance. (I am just talking about preamp-type tubes, like 6NS7s or 12AU7s.)
I haven't heard of anything like that, and I'm not sure what they would do exactly anyway.

Because vacuum tubes work in a vacuum, essentially all of the cooling of the actual tube innards has to be by radiation - you can cool the glass, but I don't think glass failure is much of a worry.

My guess is your real concern is keeping the overall unit cool enough, so I would would think about putting a small quite box fan behind the unit to ensure you've got some air circulating. If the chassis is cool enough, you should be good.

I would look at NewEgg for a case fan. They are 12VDC - you've probably got an old 12VDC wall wart or laptop PS sitting around that's more than ample to power it. The only trick is how to make it inconspicuous. You don't need to move much air at all, just enough to compensate for the cramped quarters. The primary concern is to get a really quiet fan.
Even with tube coolers the heat needs to go up. The fan idea has merit, there are some really quiet ones.
OK, thanks for the help.
Laptop fans will do the trick, especially with a wall wart power suppl. These usb powered fans, often available for $5 would be the first stop. Most are pretty quite and you can add a few to get the air flow you need in all areas of the amp. I've done this and it works well.
Check out Parts Connexion. They sell these Pearl Tube Coolers. In discussing with some folks a few years back, it was recommended to add some grounding cable from each of these to the chassis to drain any static that could occur.

BTW, the fan I linked to above is rated 8.7 db. That's pretty quiet.
Thanks everyone for the advice. I am trying to place a pair of 6NS7s in a space where there is only about 3-quarters of an inch to 1 inch from the top of the tube to the shelf above. (The rack is open on all 4 sides, though.) So I will give the Pearl coolers a try and see what happens, and try a fan later if I need to.

I am not sure how much heat 6NS7s generate, as I have not used them before. (I have some 12AU7s in a headphone amp that are pretty cool, so I was hoping the 6NS7s were cool also.)
Herbies tube coolers are very nice. I use them in all my equipment to get rid of heat from my tubes.


And he and his wife are nice people to boot...Can't beat that and his prices.
I ran across this old booklet while looking into the subject of tube coolers.

Very interesting reading about tube reliability, but fairly technical. It does seem to suggest that cooling the glass is very helpful, but only mentions blowing air on them as a strategy. It's amazing how much has probably been forgotten about tubes :)
Thanks again for that, and especially to Auxetophone for that great book! I really appreciate that great find.
Has anyone found that the Pearl PCF or Herbie's Tube coolers/dampers have helped extend the life the tubes they have used them with? I'm just curious.

Also regarding Gundam91's post about putting a ground wire on each of the Pearl PCF tube coolers. My tube amp has a ground lug in the rear. Would I connect the wire from the tube cooler to the ground lug? I'm thinking I would need to connect the wires from each of the coolers to some other metal chassis.