Ritchey Super Light Butyl 700c Tube
Ritchey Super lightweight butyl tube. Reduce rotational weight with thin wall butyl tube.
I didn't weigh them but the seem very light as you would expect but they also feel pretty tough and not too thin. I probably have 700 or so miles on them so far and issues to speak of. One thing to note is mine had smooth valve stems not threaded like in the pic and listed spec.