JBL Precision Hydrometer for the exact determination of the density in marine water aquaria. The green zone on the scale of this aquarium hydrometer represents the ideal specific gravity (S.G.) for marine animals. The precision in the green zone is better than +/- 0.0005 at 25 °C. For exact readings in other temperature ranges, a thermometer is included. The JBL Precision Hydrometer comes complete with test cylinder. Total length of the test cylinder: 34 cm, total length of the Hydrometer: 23 cm. Suitable for scientific purposes. NEW: With improved stand on the measuring vessel. The octagonal stand is considerably more stable, stands more safely and is now screwed onto the vessel.Do you have questions about this article ?