Dressing Applicator

I know these are $2 blocks of foam and you could probably cut them out for less yourself, but I don't know what foam to use, where to get, or how to cut it. So these are what I use for the application of dressing or cleaners like Sonax Alcantara Cleaner.

Generally, I'm able to do 4 or 5 cars with a single block, flipping to a new side every car.  Then I simply dispose of them and grab a new one.