Thomas Scientific Calibration Weights are solid construction and made with non-magnetic stainless steel. OIML E2 can be used as a reference standard in calibrating other weights and is appropriate for calibrating high-precision analytical balances with a readability as low as 0.1 mg to 0.01 mg. OIML F1 are appropriate for calibrating high-precision top loading balances with a readability as low as 0.01 g to 0.001 g. OIML F2 are appropriate for calibrating high-precision top loading balances with a readability as low as 0.01 g to 0.001 g. All weights include a certificate of accuracy.