Hanna Instruments GroLine 5000 µs cm Conductivity Standard with Certificate, 230 mL Disease & Pest Control Increased aeration and more drainage Foliar Applications Increased aeration and more drainage allow gardeners to more aggressively feed without worrying about overwatering these closed laboratory chillers are ideal for applications such as cooling rotary evaporators S cm conductivity standard that is prepared against a NIST traceable potassium chloride solution and supplied with a certificate of analysis Hanna's line of conductivity standards have been specially formulated to have an expiration of 5 years from the date of manufacture for an unopened bottle