5mm ID Graphite Ferrule, captive type (graphite is contained within a metal band). Used with 5mm OD Glass Packed Columns on all models of GC, Injector and Detector Stainless Steel Column Adapters on all models of GC and also Injection Port Inlet Liners on GC17 and older model GCs. 4 pack. This part replaces part number 221-15563-91, which has been discontinued. This graphite ferrule is sometimes used with the Glass Column Joint Kit, which is 221-15561-91 for installing Glass Packed Columns. This graphite ferrule is also compressed before installation on Inlet Liners, Adapters and Glass Columns using the Graphite Ferrule Compressing Parts: 221-32510-00, 221-32790-00 and 221-15561-91. (221-32510-00 is a male fitting, 221-32790-00 is Nut which threads onto the fitting and 221-15561-91 contains the back ring which fits into the graphite ferrule. These parts are also called the Graphite Ferrule Forming Jig.)