This Hydrogen Peroxide and pH Combination Test Kit tests hydrogen peroxide and pH levels. The hydrogen peroxide test is for use with a drop test system. The pH test is for use with a midget comparator. Easy to follow instructions allow for hassle free testing. Taylor formulates its reagents to remain effective for at least one year, with only very few exceptions (molybdenum indicator in liquid form is one; after four months old it should be tested against a standard periodically). As a general precaution, replace all reagents more than one year old, or at the beginning of a new testing season.