The 3.99 kit from Walmart is NOT the same as the OTO kit in the PS233; it IS the same kit that is in the HTH 6-way drops kit, which is available at some Walmarts.

The main difference is that the phenol red reagent in the K1000 / PS233 / PS200 / HTH 6-way is pH protected, and also gives somewhat more intense colors. If you use non-Taylor phenol red you will lose some accuracy at all levels, and quite a bit, if the chlorine is high.