I have a Karcher pressure washer and the Autobrite foam lance,
never had any probelms and gives good foam.
If you get a lance try and get one with a plastic connector for the lance, as they (used to anyway) come with brass ones and they stick on and are tight to move.
Jim
I have just bought a Kew washer, pick it up from my work tomorrow,got it for a very good price with a foam bottle. Will come in very handy this winter taking the salt of the cars before washing.