Designed so the specifications on surface finish, markings, construction, material density and magnetic properties get more restrictive as the weight tolerances get smaller in order to enable the weight to maintain its tolerance over time Used in extremely stable environments 1mg to 500mg are 1 piece construction with no adjusting cavity with one end turned up for easy handling 1g to 5kg are 2 piece construction with handling knob Surfaces are polished to a perfect, mirror-like finish Can be used as a reference standard in calibrating other weights and is appropriate for calibrating high-precision analytical balances with a readability as low as 0.1mg to 0.01mg