Made in accordance with API specifications and calibrated to API scale Modulus 141.5 at 60°F. All hydrometers are of precision grade. The hydrometers are constructed with a solid alloy ballast and designed to permit quick penetration to the settling point, creating no air bubbles. Scale is sealed in place by a red glass strap fused to the stem and at the top of the gravity scale even with the last number line.
Hydrometers are certified at three points on the hydrometer scale as specified by NIST (formerly NBS). In this combined form, the thermometer is provided at the bottom of the instrument with a 60°F test point correction. Each instrument is accompanied by a document of certification that includes the correction of each point tested. Instrument is 15 inches in length total.