All of the PH test reagents manufactured by Taylor, which includes TFTestKits and HTH, have FC neutralizer built-in. Of the remaining brands, some include FC neutralization and others offer a separate reagent. When the FC level is high enough to exceed the amount of neutralization, the test will read far higher than actual. The indicator is converted to chlorphenol red, which reads a different, much lower, PH range. Even when there is enough neutralization, if the FC level is fairly high, the test can read a bit higher than actual, since the reaction of chlorine with the neutralizer will raise the PH.