i cant comment on exactly how accurate they are but ive never had a problem with them. and i think PFK (uk fish mag) gave them a good write up a while back.
there very convienient, just a shame they dont have ammonia on there too.
oh, one thing, make sure you obey the 'dip then leave for 60 seconds' or whatever it is as it can make a big difference in readings.
all the best.phil
