Essentials CF Standard (CF 28) 2.8ms is a 30ml sachet, single use CF/EC solution to calibrate CF/EC meters.

Essentials pH buffers are a known solution of a certain pH value designed to test the accuracy of pH meters used to measure the pH of a nutrient solution. Essentials buffers use two values of 4 and 7pH to calibrate your pH testers as they are at the outer reaches of the range of pH where you work in hydroponics i.e. 5.5-6.5