Columns from 10.5mm I.D. to 22mm I.D. have a 2mm PTFE stopcock. Sizes 29.5mm I.D. to 49mm I.D. have a 4mm PTFE stopcock. Coarse porosity sealed in disc. Other column sizes and disc porosites as well as outer standard taper joint sizes are available. (MICRONS – inchF inch (4 to 5.5) inchM inch (10 to 15) inchM/C inch (30 to 40) inchC inch (40 to 60) inchC/EC inch (70 to 100) inchEC inch (170 to 220)