When glass is used for both the stopcock body and the plug, the contacting surfaces between them are special ground glass surfaces (see Laboratory glassware) often with stopcock grease in between. Special glass stopcocks are made for vacuum applications, such as in use with vacuum manifolds.
When glass is employed for both the stopcock body and the plug, their contacting surfaces are special ground glass surfaces (see Laboratory glassware) often lubricated with stopcock grease. Special glass stopcocks are designed for vacuum applications, such as those used in vacuum manifolds.