Sensory Stones - Set of 8The set of eight stones includes four raised designs (circles, dots, wavy lines and a grid) and four indented hollow designs (circles, lines, zigzags and a spiral). Dimensions 7cm (3") H About Learning Pebbles Appealing to children's natural instincts to sort and collect, these tactile pebbles can be used in sand, water and small world play. Cast from a unique mix including real stone, they are durable and waterproof, so they are ideal for use