These pads can be cleaned and reused. The type of cleaner used to wash them will be dependent on the type of paint used.
Get a paint pan and fill it til the bottom reservoir is full. Dip the pad in, then mush it down on the "washboard" area above the reservoir and you will see the excess stain leach out of the pad. I found that when I applied my stain quite generously on my deck boards I had very little waste. The pad, when it's not falling off the frame, does a good job of applying the stain.
LIFT THE TAB UP TO ALLOW THE PAD TO SLIDE ON THE HOLDER. IT LOCKS INTO THE GROOVE ON THE PAD
I'd be reluctant to use it for interior painting. Perfect for more rough deck staining, handles nail heads relatively well, but take the time to pound them down before using the applicator.