OIML Class E1 offers high accuracy with tight tolerances and guaranteed uncertainty 1/3 of the tolerance. Weight surfaces meet or exceed OIML R 111 and have a highly polished mirror-like finish. Weights 1g – 20kg are made of Troemner Alloy 8 Stainless Steel which possesses closely controlled density (8.03 g/cm3), extremely low magnetic properties, good stability, and resistance to corrosion. Weights are supplied in high quality cases to ensure weights are held securely, kept clean, and dust free. NVLAP Calibration Certificate is accredited to ISO 17025 which is recognizable through ILAC. Individual Calibration Weights Adjusted to Meet or Exceed OIML Class E1, E2, F1, and F2 Tolerances