G&W Hydrometer Specific Gravity 1.000-1.050 - Hydrometer suitable for checking Specific Gravity changes between 1.050-1.100 during fermentation. This Hydrometer has been calibrated in accordance with the A.S.T.M. standard E 126 and N.I.S.T. circular No.555.The instrument is traceable to N.I.S.T. having been calibrated against an instrument has been certified by the National Institute of Standards and Technology. If the Instrument is an A.S.T.M., it has been manufactured to meet the A.S.T.M. standard E 100.