The most common materials found inside commercially made stress balls are a type of gel or foam. These stress balls are made from a strong, durable rubber .
The resulting chemical reaction creates carbon dioxide bubbles as a byproduct, which in turn creates the foam. Stress balls, especially those used in physical therapy, can also contain gel of different densities inside a rubber or cloth skin. Another type uses a thin rubber membrane surrounding a fine powder.
Gel stress balls provide a therapeutic option for releasing stress or pent-up. The inside of the ball is filled with a silicone-based gel, sometimes infused with .
Whats inside the stress ball? Air, sand. it feels like some kind of liquid / gel stuff inside.. The package says the ball is filled with a non-toxic, water-based gel.