The Extech EC-12880-P Conductivity Standard (2 Bottles - 1 Pint Each) are two bottles of 12880µS Conductivity Standard, 1 pint each of premade solution. EC-12880-P is for use with Extech Conductivity meters like the EC400 ExStik Conductivity/TDS/Salinity Meter or DO610 ExStik II DO/pH/Conductivity Kit.