Ferrofoam 424 is a specialized polyurethane foam that expands by approximately 20 times when it comes into contact with water. It offers moderate flexibility, making it highly effective for stopping water leaks in basements, water tanks, and dams.

Its use with a high-pressure injection machine allows it to penetrate deep into concrete voids and cracks. It then expands to create an excellent and durable waterproof seal, which is more effective than traditional water plugs.