Over the past 3 months i have bought 2 complete api reef test kits, and 2 complete saltwater test kits all master kits...i do complete testing everyday doing this research and out of 88 days i only had 14 days that any two kits tested the same, i used timers, and went by their book to a "T"...I even got 1 of the kits that has different color charts go figure , thought maybe it was something new, but after lookin it was the second kit i bought, All bottle are newer than 3/09 so all should be good.. one of the pics im going to post is two of the kits tested at the same time, same water ,same test, 2 different readings, notice the difference in the charts!