What exactly are these?

This week we have replaced two of these 'scale reducers' with proper block salt twin cylinder softeners.

These new houses in the purbecks had come with these 'devices' fitted, but it soon became clear to the new house owners that they had no useful benefit and their kettles, showers and taps were furring up. 

We quickly took them out and fitted proper water softeners guaranteed to take out scale.