Excellent teaching resource to stimulate learning related to the physical and social environment. Made of flexible, durable plastic with non-removable safety wheels. Reusable containers. All with silent wheels. Each jar includes 1 dump truck, 1 digger, 1 rescue, 1 police car, 1 fire truck, 1 ambulance. Vehicles measure 4.25″. For ages 8 months to 3 years.