Tubolito Mountain Bike tubes, an Austrian company that makes tubes which are freakishly light. Getting past the weight alone, the company also claimed that they are twice as robust and resistant to flatting.
Compared with a normal tube:
And the size. The one to the right is the S-Tubo-MTB, even thinner and with a detachable valve.
The removable valve in detail:
Here’s the packaging:
The prices are 29.90 EU for MTB.