Alex it's the green bristle square ungar brush I used. I've used it for years with my hot wash but thought I would try your brushes as I know they were lighter of which they are. I did mention to one of your staff about the brush I use and its a good brush but abit heavy, I asked what's the similar brush and was told that your brushes are not the same but try the dual trim brush where I asked for the stiff bristle brush. I bought two. Where I change the jets as I like the hexagon 2mm pencil jets the plastic framing on your sill brush isn't as wide, so when I drill out bigger hole I lost quite alot of brisstles. I did the same on the other normal square dual trim but that was fine. I find that I have to really keep scrubbing for ages to get stubborn muck off but only scrubbed a little with the ungar brush. The brush is heavier but makes the pole more sterdy I find. The good thing about your brush being lighter is that it don't hurt your neck and shoulder as much at the end of a hard day !!!!
As the years go by the weight of various components do become very important. I started out with a 6.5kg 30ft pole and a 900g brush - after two years, 5 days a week, I was starting to notice it! (still got this pole/brush tucked in the garage for posterity)
For some the weight of a brush is not significant, but with repetitive use for most of us it does become a factor in our general health. Hence our focus on low weight which has helped bring the industries general weight of products down.
If you are using an older green Unger (originally a Vikan) rectangular brush then the nearest you would get in scrubbing power would be the Super-Lite DT Medium-Mixed or the Super-Lite DT Flocked