There are two power settings available, low and standard power. The low power is used where concrete strength is less than 3000 psi (19.4 MPa). The newly designed silver probes can be used for high performance concrete with strength up to 17000 psi (110 MPa). The probes are made of a high strength alloy, specially heat treated and annealed to achieve a hardness of Rockwell C 48.Special machining of each probe eliminates stress concentrations. The silver probe is used with concrete having a density greater than 125 lbs/cu. ft. (2003 Kg/M3). The Windsor Probes are available in Bulk discounts This package contains one pack of three. ASTM C 670