Q-tubes is the house brand of one of our favorite distributors, Quality Bicycle Parts. The tubes are high quality, produced by Kenda. They are black rubber with a 32mm Presta Valve. At ~182g/per, they're light, but not too light if you know what we're saying. While they state 26" x 1.9-2.125", plenty of us with 2.35 tires run them without a problem.