These combined-form hydrometers, with a convenient, built-in thermometer, come in a wide range of models measuring the relative density specific gravity of oil and petroleum related products in various ranges from -1 to 101°api in accordance with american petroleum institute api standards. conform to the accuracy requirements for astm thermo-hydrometers lead free ballast and glass 381mm 15 long temperature standardization: 60°f 15°c thermometer contains mercury-free blue spirit organic liquid fill with a temperature scale of 0/150°f individually serialized hand inspected by our u.s. Quality team packaged with a multi-language english, french, german, italian, portuguese, and spanish statement of accuracy indicating accuracy traceable to nist note : combined form thermo-hydrometers should be stored in a clean, dry, safe place, and should not be subjected to extreme temperatures. Built-in thermometers should be used as a general reference only. For temperature critical applications, a calibrated standard thermometer is recommended.