I'm just using these by themselves, without any holder. At $5 each it's a great deal. They work as you'd expect. They're thick enough so that you could even cut them in half and get 4 double-sided cat scratchers.
I ordered these because I like the idea of only replacing the worn board, and not the entire thing. Unfortunately, they don't fit in the scratchers I already have, which is totally a lack of reading on my part. So, I just set them on the floor and the cats use them flat, but I would prefer a replacement that fits...or even to be able to find the scratchers that these fit into. No complaints other than operator error. I would recomend these if you have the correct scratcher. They are solidly made and a good price.