VEE GEE Scientific Alcohol Hydrometers measure using the Tralle and Proof scales. Model 6612-1 includes ranges 0 to 100% Tralle and 0 to 200% Proof. Approximate length is 305 mm. Model 6612-2TS includes ranges 0 to 100% Tralle and 0 to 200% Proof; also includes an internal thermometer for measuring solution temperature from -10 to +100°F. Approximate length is 355 mm.