Just one emendation: the 6-way does not READ higher than 5 ppm, but it does INDICATE higher levels, by a transition from dark yellow (~10 ppm) to orange (~30 ppm) to brown (> 60 ppm).

This is a VERY important difference from the DPD color match tests, which can bleach out and read 0.0 at FC levels as low as 15 ppm! Before we began pushing OTO *or* DPD-FAS kits, we used to have lots of problems with people adding more and more chlorine to their pool, think they had none, when in fact it was way too high.