Surface Performance Gmax testing in Greenville, Alabama measures two things, absorption and impact. A 20lb missile is dropped in 10 locations on the field, three drops per location. The missile measures G forces upon impact which provides Gmax values for the surface. The higher the Gmax value, the less force is absorbed by the playing surface. Surface Performance couple Gmax testing with HIC testing to gather additional information to provide a fully in depth report on the pitch performance and user safety. HIC testing is the internationally recognised test for head impact injuries.