The Bel-Art Scienceware 420400000 replacement stopcock is to control airflow into and out of a vacuum desiccator, for use with Bel-Art Scienceware desiccator models F42025, F42020, F42010, F42012, F42022 and F42027. The body of the stopcock is constructed of polypropylene for strength, thermal performance, and solvent resistance, and the plug and washer are constructed of polytetrafluroethylene (PTFE) for strength and resistance to moisture and temperature changes. The stopcock's taper fits on the desiccator port to provide easy, leak-proof turning. This item can be cleaned using a soft cloth and standard laboratory cleanser. The stopcock's plug has three positions: vacuum draw, shut-off, and vacuum release.

Desiccators are sealable containers used to remove water from a sample, or to preserve moisture-sensitive electronics or lab consumables, typically in laboratory, electronic, and aerospace applications. Desiccators are often used with desiccants, which are drying agents such as silica gel or activated charcoal placed under a removable platform. Standard desiccators are typically lidded jars used with a desiccant. Vacuum desiccators have a stopcock that allows air evacuation from the desiccator. Gas purge desiccators use a gas port to introduce nitrogen or other gasses, creating a controlled environment. Vacuum and gas purge desiccators may also be used with desiccants. Many desiccators are used with vacuum grease, which helps create a seal.

Bel-Art Products manufactures scientific products, including labware, testing equipment, and safety supplies, under the Bel-Art and Scienceware brands. The company, founded in 1946, is headquartered in Wayne, NJ.