Laboratory condensers are large, coolant-filled tubes that surround smaller glass tubes that contain a hot fluid or vapor. They are used to cool fluids and condense gases. Lab condensers are used mainly in distillation and in reflux, where the hot solvent vapors of the liquid being heated are cooled and allowed to drip back (thus reducing the loss of solvent). A type of glassware, they do not contain electrical components. Product categories include Liebig, Allihn, Graham, Friedrich, Dimroth, Vigreux, and West condensers; double cooling, reflux coil, and dry ice condensers; and both air condensers and water condensers. When selecting products, buyers may choose laboratory condensers that are graduated and/or have ground glass joints.