Bluelab pH Pen — Handheld pH MeterBluelab pH Pen The Handheld Standard The ultimate hand held pH meter for growers accurate, robust, and simple to use. The Bluelab pH Pen is the pen most UK growers settle on after trying cheaper alternatives; Bluelab's reputation for accuracy and probe longevity is well earned. Tells you exactly what your nutrient solution pH is, in two seconds, with one hand. Why growers choose the Bluelab pH Pen: Industry standard accuracy Bluelab is the reference