DD-D is a Shore D durometer or hardness tester used to measure the Shore hardness of materials such as hard rubber, hard resin, acrylic, glass, thermoplastic and more. This Shore D hardness tester uses an impact rod with a 30 º conical point and 50 Newtons (N) of force to make a surface indentation on material samples with a minimum thickness of 6 mm or 0.24". (Note: If a material sample does not meet the minimum thickness required, the sample should be reinforced on the back with more of the same material.)