UCEC Calibration Weights for Digital Scale, 10mg - 100g Gram Weights Kit, Precision Stainless Steel Balance Scale Calibration Weight Set with Tweezers for Lab Educational Science

All is good except for the tweezers to handle the metal weights. They are made of cheap plastic and don't have a good grip.

Quality is great weight is perfect accurately.

Only giving them 4 cuz I have no reference to check their accuracy. The little ones showed me my mg scale is off a little or they’re off a little, not sure which. For the price, they were good enough for me and what I’m doing.

I should preface this review by saying that I do not have access to a calibrated lab scale with mg accuracy, which is what I would use to determine the accuracy of these weights: use them with a scale of known accuracy with lab-quality calibration. HOWEVER... I got them to test the sensitivity and accuracy of a small consumer-grade electronic scale that I bought here, which claims to be sensitive down to the nearest milligram. For 30 bucks, this is quite a bold claim, given that the ones that you'd use in a proper lab cost thousands of dollars. But I got these weights and that scale at the same time, and then followed the procedure for calibrating that scale using the two 10g weights it came with. Now this set of weights comes with a set of 1gram and above weights, all of which my little scale came in within about 5mg of the nominal value. It was the set of under a gram weights that I was wondering the most about. This set has 500mg, 200mg,100mg...all the way down to 10mg. Rather than taking the familiar form of a small silver metal cylinder, these weights are smallish metal squares. Some reviewers complained that these squares arrive all bent up, but that's a feature, not a bug. The upturned corner makes it easy to grab with the tweezers even when the rest of the weight is flat on the surface of the scale. Which you definitely want to do, because if you even breathe hard on the smallest weight its liable to go flying off into the cat dimension, never to be seen again. Anyway, I was able to determine that my little scale does have milligram level sensitivity, however, the accuracy of it is probably +/- 5mg. Which is fine for my purposes, because for the stuff I am working with, I need to measure small amounts of stuff in the 250mg total weight range. So if what I can get is 250mg +/ 5mg--so long as the error is relatively small and more importantly, known accurately--one can usually work with that. If the level of your need for accuracy is truly down to the single milligram level, then you're going to want to pony up the money for a lab-grade set of calibration weights, and you're going to pay at least ten times the money that these weights cost.

Great little set of calibration weights. The only reason im giving it 3 stars is because the plastic hinges on the lid are already stressed to the point of breaking off which will happen very soon.