Calibrators quickly field-check accuracy of pressure-type concrete air meters. With a calibrator in the water-filled base, air meter gauge should read 5% air. Two calibrators are used in a 0.25ft? meter for a 10% air reading.

HM-25 Plastic Calibrator is rugged plastic with metal weighted ring. 3.75x4in (95x102mm), HxDia. Est. Ship Wt.: 3lb (1kg).