They are made of a super grippy PVC material that even a small child can grasp with one hand. The Gerties feature a unique valve for inflation to various levels making it even easier for smaller hands to grab and squeeze. Also perfect in an adult setting where arthritic hands are not able to react and grab as tightly as they once did. Nobbie Gertie Balls add an additional tactile element. Made of a non-toxic PVC material (not latex).