Rice Lake 12504 20 Piece Stainless Steel Calibration Metric Test Weight Set, 50g - 1mg Size, NIST Class F Metric, NIST Class F calibration weight set for calibrating other weights, or electronic balances and scales Stainless steel construction for stability, resistance to corrosion, and low magnetic susceptibility Meets National Institute of Standards and Technology (NIST) Class F specification for commercial "Legal-for-Trade" weighing operations Set of 20 weights includes two each 20g, 2g, 200mg, 20mg, and 2mg weights, and one each 50g, 10g, 5g, 1g, 500mg, 100mg, 50mg, 10mg, 5mg, and 1mg weight, tweezers, and a protective case