These neoprene rubber stoppers are supplied in a pack of 10, with each stopper featuring a single hole. They are blue in color. Each stopper measures 6 mm at the bottom, 8 mm at the top, and 16 mm in length. The neoprene rubber construction is suitable for use with petroleum products, minerals, oils and fats, as well as most inorganic acids and bases. The single hole allows for the insertion of small-diameter glass tubing or thermometers.