Improves balance: These stepping stones are great for developing your child's mobility and coordination.Stackable: When finished, these kids stepping stones can be placed on top of each other, saving space.Durable material: Smooth, durable and safe to use - kids will enjoy playing with these river stones.Non-slip bottom: Comes with a mat that needs installing – keeps these sensory stepping stones secure, even on smooth surfaces.Dimensions: Small: 4.5H x 24L x 14.5Wcm. Medium: 7.5H x 33.5L x 20.5Wcm. Big: 16H x 38L x 24.5Wcm. Large: 20H x 42L x 31Wcm. Suitable for ages 3-8 years. Assembly required.