These are replacement glass stopcock plugs for No. 7280 PYREX® straight bore glass stopcocks. Since several different bored sizes may be drilled through any given size of plug, the approved method of designating the size of a glass stopcock is by bore diameter only. Interchangeable ground glass stopcocks are not intended for high vacuum apparatus or for use with light liquids. When, by constant abrasion, a stopcock has become so worn that the shell is enlarged, or the plug is diminished in size, we recommend that you replace the plug.