cases vacuum. Stopcocks plugs are generally made out of ground glass or an inert plastic like PTFE. The ground glass stopcocks are greased to create an airtight seal and prevent the glass from fusing. The plastic stopcocks are at most lightly oiled. Stopcocks are generally available individually with some length of glass tubing at the ports so that they can be joined by a glass blower into custom apparatus at the point of use. This is especially common for the large glass manifolds used in high vacuum lines. Many additional variations exist in both plug boring and joint assembly. Types 1-, 2- and 3-way stopcocks Needle valve stopcocks straight or right-angled Burette stopcocks straight or lateral Desiccator stopcocks Vacuum stopcocks one-way straight or parallel, one-way right-angled or 2-way Gallery External links References Plumbing valves Laboratory glassware ru:Задвижка