A good idea, but useless in practice. Very lightweight and runs on a roller at the front of the unit. This seizes when the slightest bit of grit adheres to it, making the unit pitch forward. Likewise, pulling it back, the unit tips backward on its brush skirt. Therefore, it only works well when not moved!
It does reduce spray compared to the normal wand, but even on a patio with an even surface, it can't be moved easily so is frustrating to use. I've tried it twice and after getting no help from Bosch customer services - quote "don't know what to say, you shouldn't have bought it", it is now in our local charity shop!
YOU HAVE BEEN WARNED, DON'T BUY THIS PRODUCT!