I have only ever used the Envirodri gen 4 since i started last year and from what i read on here it appeared to be an essential piece of kit so i got one, i imagine it takes the hard work out of using a grooming type brush which i find poor in comparison, the only down side to it is the weight , changing the brushes and cleaning the thing i have also found that it can leave marks in some carpets i did a job last saturday and it left marks that were difficult to get out but they came out with multiple passes with the wand and i was using the softest brushes availlable the gold ones

i have the stiffer white ones and some white and gold suppose these are for damaging a carpet a bit less :

never understood why they made them or why i got them seemed a good idea at the time with hindsight a waste of money