I like them but they're not completely foolproof. As in, I broke the little glass vial after about 3 tests. (Whee! $10 per test, I rock!!) You can't buy replacement vials.
If it had been plastic it probably wouldn't have broke so easily, I dunno.
Other than that, seem like pretty good test kits. Strength seems to be in the low range readings. Course with one tank at 80ppm I'm at the wrongggggggg end of the scale on that one, but I'm trying to deal with that problem. I shouldn't have let it get so bad before trying to deal with it.