ASTM Class 0 calibration weights are primarily used for calibrating other weights and standards. They are primarily used in metrology labs and are a solid one piece construction. This means there is now way to adjust the weight later on. That is why ASTM Class 0 weights must have a stable environment with careful handling. They are not intended for use in general laboratories but can be utilized when the highest level of accuracy is required. They can be used for calibrating ultra micro balances, micro balances, and semi micro balances. For more questions about calibration weights and what kind would be best for you application, please contact us. You can reach us through the livechat, via email at firstname.lastname@example.org, or by calling 616-622-2100.