The Method is based on the principal that the rebound of an elastic mass depends on the hardness of the surface which it strikes. The Test is fast & unlikely to cause damage to the concrete.The hammer is intended for testing the quality of concrete in finished structures such as buildings and bridges. Supplied complete with carrying case and carborundum stone, the hammer is suitable for testing concrete with Compressive Strengths of 10 to 70 N/mm2. Weight 1.4 Kgs. App.