The Extech EC-1413-P 1413 mu S Conductivity Standard (2 bottles - 1 pint each) are two bottles of 1413 muS Conductivity Standard, 1 pint each of premade solution. EC-1413-P is for use with Extech Conductivity meters like the EC400 ExStik Conductivity/TDS/Salinity Meter or DO610 ExStik II DO/pH/Conductivity Kit.