2 years & up. Smooth-sanded, over-sized beech wood Jumbo Sensory River Stones feature inset, nature-inspired textures. Children can engage in sensory play while practicing stacking and balancing and strengthening their tactile differentiation. A beautiful, subdued color palette furthers the possibilities for organic connections during natural play. Smallest stone measures 5.125"W x 2.5"D x 1.125"H, largest stone measures 7.625"W x 3.75"D x 1.75"H.