12 or 18 inch,had a accident on tuesday lent my tucker pole on the window ledge went to the van for a minute came back and the wind had blown the pole down,snapped a 12 inch brush,so went to the van to find replacement brush but i only had 18 inch so put this on instead,covers the window more and you can be quicker,but it is heavier to work with,what do you use for domestic work.