Graphite/vespel ferrules (15% graphite/85% polyimide) are recommended for use with GC/MS systems. Best choice for glass columns and polyimide-coated, fused silica capillary columns. Can usually be removed easily from column. Temperature limit is 350°C. Note: 0. 25-0. 32mm inner diameter. columns require 0. 5mm inner diameter ferrules. 0. 53mm inner diameter columns require 0. 8mm inner diameter ferrules.