We sell a range of metal weights for calibrating scales at Gravitation. In addition to cast iron and brass weights, we also have a full set of F1 weights. Scale calibration weights vary in type depending on the application, but a good general rule of thumb is to use M1 class weights for scales with a coarse resolution of 0.1g, 1g, and over, F1 class weights for scales with a fine resolution of 0.0001g and E2 and