Adapter has the listed size of Chem-Thread at the top for a vacuum tight seal of a variety of tubing diameters. Will accept glass, metal or heavy wall plastic tubes having diameters between 7 to 18mm O.D. such as thermometer wells, gas dispersion tubes, plain stem funnels, etc. Serrated hose connection has an O.D. of 10mm at the largest serration. Adapters are supplied complete with a Celcon® compression cap and Viton o-ring.