I have a garden hose with variable spray patterns, like this. It consists of a disk with different holes arranged circumferentially. This fits up against a seal (in my case, an o ring (24)). Unfortunately it's hard to get a good seal against a sliding surface, so, not surprisingly, after a few hundred usages, the seal wears and starts leaking. Whoever designed this just doesn't understand mechanical engineering (also, look at the sharp directional change in the feed pipe, for no reason).