Etekcity 0.1pH Resolution High Accuracy Pocket Size Handheld pH Meter Pen Tester, Yellow Great for all pH testing applications including aquariums, swimming pools, tap water, beverage etc No calibration needed for new units. Easy to calibrate with pH 4 & 6.86 buffer packets included 0.1 pH resolution; With LCD display, measure & display pH results simultaneously Handheld pen-type design for portability and convenience with carrying case The electrode can be used in particularly taxing conditions; CE/FCC/ROHS Approved