that gemini scale ( I believe the one where they recommend that you put a dime on it) is not very good. I purchased the one above that, it retails for around 200 bucks and it used to sale on amazon for 55 bucks, now its almost a hundred. But, when your dealing with .001 resolution you get what you pay for. Also remember, to use it away from all computers, cell phones, tv's etc. and get some test weights, After calibration, i have a 10mg weight all the way up to 10grams. I've seen it be off by only a couple milligrams at the most.. Its worth it to pay a little extra to get a good one... But that gemini one that needs a dime to make it work should be avoided...