Stone Dish Drying Mat

Really like this product. I accidentally threw out the sandpaper so I am wondering what kind I should purchase. Also One side has a clear plastic. Am I supposed to leave that on? Thanks for your help.

Product not as advertised. Produt stains! Water held with plastic backing. Top dries but water underneath Plastic mesh stains underneath on bench.

Just what we needed to have next to the sink. Looks good but also functional.