light 29er tubes
Performance Lunar Light, 26x1.95-2.25, three for $25, weigh 95-100gm, very stretchable, just pump them up a little and don't really need to be stretched, only takes a couple of psi (too low for my guage to measure) and they fill a Nano. Obviously thin, wouldn't want to use them where there are a lot of thorns, but they have worked as well for me as any others as long as I check the pressures to make sure I don't get too low and start pinching them. A Continental 28x1.75-2.5 is obviously tougher, but weighs 235gm. YMMV
