... borosilicate glass, heavy wall. glass stopcock or PTFE stopcock3:Size:Column I.D(mm):16, 22, 30, 40 Effective length(mm ... Teflon stopcock and a top outer joint.for flask chromatography.since the chromatography colum is used with positive air pressure,it's ... highly recommended that operator uses colum behind a safety shield. Column,chromatography,rodaviss joints,teflon stopcock