Long enough to reach every inch of your containers.
I own several water bottles, sodastream bottles, and thermos bottles that require frequent scrubbing in order to avoid unpleasant smells and tastes.  These brushes are perfectly what I needed to reach the entire length of the bottle.  The width of these brushes allow them to be used on bottles with narrow mouths yet also reach the walls of sodastream bottles.  I can see these brushes also being invaluable in cleaning baby bottles, or to have have one at the office to clean your water bottles at work.  The brushes are flexible allowing you to angle them to reach every inch of the interior surface of your containers.  Highly recommend for sodastream users.
Rating: 5 stars