The design of the neck has a flared mouth to form a water seal which prevents the entrance of air

·         For reference see Method 5210-C: Ultimate B.O.D. Test (22^nd Edition of Standard Methods for Examination of Water and Wastewater)

·         Manufactured from 33 expansion, expansion, low extractable borosilicate glass conforming to USP Type I and ASTM E438, Type I, Class A requirements