These are quality inexpensive tubes. The valve stem is threaded all the way to the base and there is a nut that goes over the threads. This gives you the ability to secure the valve stem in place making installation incredibly easy.
Normally have great luck out of continental tires and tubes. But the first tube I had blew up while inflating at just over 40 psi. Had to run to the local bike store and pay twice the price for a lower quality tube. Kind of disappointing, but the other three held.
I got these tubes to match with some Continental tires bought at the same time. While I was installing the first tire, the tube blew out at about 50 psi, about a 4 inch long split. Could have been pinched, or a one in a million defect, I don't know. I never had a tube blow out like this before in 40 years. But since this was for my wife's bike I switched for some older Specialized tubes I had on the shelf that were a bit thicker rubber.