Supports the following standards: ASTM D4318, ASTM D2240, AASHTO T89, AASHTO T90 As required by ASTM D4318, a durometer is used to test the hardness of the base of a liquid limit machine. Sealed springs maintain load deflection rate to a tolerance of .0004". H-4222D is used to check the hardness of the base of Liquid Limit Machines and complies with ASTM D4318, D2240.