Very well made, convenient size, and easy to use.  The hold button allows measuring when the scale cannot be directly read.  It does an excellent job of measuring the quality of water processed by reverse osmosis, but it did not accurately measure water hardness that is processed by ion exchange.  Internet literature hinted that it would, but since these softners exchange ions and do not remove solids, It is not the meter's fault.  There is no manual to explain what it does and what the readings mean.  Instructions are written on the box which is not easy to store.