This unique kit has everything you need to introduce your students to the challenging concept of density. Experiment to demonstrate that different objects with the same volume may have different densities. Kit includes two cube casings with flexible inserts, two cylinder casings with flexible inserts, two cylinders, plus ping - pong balls and cotton balls for additional demonstration and an Activity Guide. The versatile, plastic casings also can be used to hold other common materials such as sand, water, popped popcorn or rice.