250 gram Scales USA Scale Test / Calibration weight OIML M1 (250 grams) Use this Accurate Weight to test or calibrate your scale. A Manufacturers certificate is included with each weight giving the accuracy information. (This is not a NIST tracable certificate) A plastic protective case is included to store your weight and certificate. The weight is manufactured to meet the weight accuracy requirements of OIML-R111 Class M1. The 0.008 gram accuracy is suitable to calibrate a scale to 0.025 grams. Although you can use the weight for lab or home use scales, class M weights are intended for use in the calibration of weights for use with weighing instruments of medium accuracy class III and ordinary accuracy class IIII. They can also be used as control weights and are usually accompanied by a calibration certificate.