[Wikipedia excerpt: ‘… Glass tubes (“G.T”) are mainly cylindrical hollow-wares. Their special shape combined with the huge variety of types (like borosilicate, flint, aluminosilicate, soda lime, lead or quartz ), allows the use of “G.T” in many applications. For example, laboratory glassware, lighting applications, solar thermal systems and pharmaceutical packaging to name the largest. In the past, scientists constructed their own laboratory apparatus prior to the ubiquity of interchangeable ground glass joints. Today, commercially available parts connected by ground glass joints are preferred; where specialized glassware are required, they are made to measure using commercially available “G.T” by specialist glassblowers. For example, a Schlenk line is made of two large “G.T”, connected by stopcocks and smaller “G.T” , which are further connected to plastic hoses.
…..”G.T” are produced in various types of glass and in diameters ranging from a few millimeters to several centimeters. In most production processes, an infinitely long “G.T” is drawn directly from the melt, from which approximately 1.5 m long pieces are chopped off after passing a roller track up to the drawing machine…..’ ]