I forget the actual model number, but the one to get is made by Gilmoure (SP?) and features a brass bar with different size holes in it for selecting the dilution. I've seen them labeled Butcher's, Simple Green, and something else I can't recall.
I'd order from Danase but AutoGeek has them too.
Read up on how we modify/optimize them with shutoffs and quick-disconnects as well as how we use them.
I need very little "rubbing" effort from wash my car once it has been foamed. Makes the wash mitt slip and slide effortlessly over the bodywork. Also as other have said the resultant wash is better as the foam has helped “soften� contaminants by being allowed to sit on the car for a few minutes.