Well, buy the wave first, because it comes with 14 of them, and then when you need to go get your refills use the coupon inside the box.
There's 30 pad thingies in the refill box, and it comes with a new attachment head.
So about every 2 weeks you'd need to get a new box if you used it everyday, twice a day.
I don't listen to the instructions, and I use the other side of the pad.