This is my second purchase of a surface cleaner but the Westinghouse unit (with plastic housing unlike the stainless steel version depicted) is far superior to my first cleaner (non-Westinghouse brand) due to the castor wheels making it easier to move the unit back and forth.
This worked great to remove the moss between my patio blocks. Instead of dealing with streaking from using a spray wand, this keeps a consistent spray pattern on uneven surfaces. Before using this attachment it would take me about 2 hours to clean my patio, with this I was able to complete the job in less than 45 minutes.