Carbon fiber tank weights 50% less than aluminium one but holds twice as much O2.
Go to the bottom to get specs comparison:
http://www.michiganinstruments.com/Thumper%20Mobile%20Oxygen%20Specifications.htm

It is pretty amazing but on expensive side. DD size tank will run you about $450. I handled one last week at the buff show for EMS and I wouldn't mind carrying it at all. Great tool for search and rescue or whenever space is limited and you need more Oxygen.

Matt

Wow, very impressive specs indeed on those O2 tanks. 'Tanks for the link!