Take a look at this thread: http://www.autogeekonline.net/forum/auto-detailing-101/90986-do-i-need-foam-canon.html#post1244365
Also, as someone mentioned, there are two different ones. There is the MTM 14.0263 for gas pressure washers and 14.0349 for lower pressure (up to 2600 psi) electrics...