Core training, balance. For indoor play, educational toys. It's clean after just a little play. This type has non-slip pads on the entire underside, so it's safe and won't slip even when jumping. The top side has bumpy footprints for grip. Extra large: 1 Large: 2 Medium: 4 Small: 4 Total: 11 pieces. These are balance stones in soft, gentle colors. Everything in the photos is included. Please check the photos for dimensions and condition. Please understand that these are used items before considering a purchase. Thank you.