Like most other Mountain Bikers, I ride tubeless tires and only carry a tube in case my tubeless system fails on the trail. I like Continental's tubes for this purpose since they are made to fit wider tires and have a nice long 42mm valve. Some other tubes have a 32mm valve that can be too short for the wider-and-deeper rims that are on a lot of newer bikes.
Great tube to carry on the trail for unexpected flats. I use a voile strap and keep one attached to my bike any time I'm doing a longer ride. They are also quite a bit cheaper than other alternatives and seem to be just as good.
Continental makes great products and this is no exception. These tubes hold up to abuse and are less expensive than many other options that are very similar. If you are looking for an extra tube to carry along on your ride these are a great choice.
I run all Continental tubes in my road bikes and knock on rubber I haven't had any issues in my thousands of miles of use, so when I needed a spare tube to run on my MTB in case of a failure this was the obvious choice. Thankfully I haven't needed to use it.