They resemble to stones, but they are not! The RIPIETRA tiles by Angelo Grassi are one of our top choices for the  outdoor (and indoor) applications and are made out of completely natural material which is produced by extrusion and moulding and is 100% recycled and recyclable. The surface of the tile has a built in rough texture that helps create a highly anti-slip surface! Their shape will permit you to set them according to your own taste!