I have deep V rims so I need long stem tubes. Around here you really can only get Specialized or Continental tubes at the LBS and they are cheap enough that it is not worth getting them online. I usually get 700x18/23 since I ride 23 tires, both tend to come with threaded presta valves. I like the continentals better they seem to resist flats better (might be my imagination) and I have less problems getting the pump to seal on the valve that the Specialized (not my imagination). Seems with those I alway get air leaking and I have to reseat the pump head 2-3 times to get up to pressure.