A Schlenk filter consists of sintered glass funnel fitted with joints and stopcocks. The viscous one is used for standard stopcocks and ground joins. The plastic stopcocks are at most lightly oiled. To prevent explosion the stopcocks were opened and the magazine flooded. Special glass stopcocks are made for vacuum applications, such as in use with vacuum manifolds. Stopcocks used in laboratory glassware are typically forms of conically tapered plug valves. Stopcocks with glass barrels need to be lubricated with vaseline or a specialized grease. Stopcocks plugs are generally made out of ground glass or an inert plastic like PTFE.