LABO API Combined Hydrometer, 19/31, 40/60, 30/90, 49/61, 60/90, 30/50, 9/21, 39/51 Thermometer Range: 0-150F What is API Hydrometer? API hydrometers have multiple ranges that are precision grade for measuring API gravity of crude oil and other petroleum products. LABO Techonology offers all ranges that comply with API (American Petroleum Institute and The American Society of Testing Materials (ASTM) E100 standards, from -1 degrees to 96 degrees. Made in China or USA. API Hydrometers are calibrated at 3 API points: Low, Middle, High