Activity Blocks by PlanToysActivity blocks by PlanToys. This set of 9 sensory blocks consists of 3 visual blocks, 3 auditory blocks and 3 texture blocks. Storage bag included. Each block is 3. 5cm square. Made from natural rubber wood trees that no longer produce latex. To keep the wood pure, no fertilizer is added to the soil three years prior to cut the trees down. To strengthen the wood, PlanToys uses a chemical free kiln drying process. All PlanToys are made using certified