Kimble 17800 KIMAX Glass Chromatography Columns with PTFE Stopcock have a reinforced top and tooled lower end taht provides extra strength and a tight, leakproof fit with all-PTFE stopcock. An "O" ring has been added under the PTFE fitment to maintain a liquid tight seal over a large temperature range (0-100 °C). Liquid contacts only glass and PTFE. Stopcock is easily removed, providing easy access to column packing. Tip and stopcock assembly are available as replacement components. Replacement stopcock for all sizes is 41006F-2.