Vespel® ferrules are made from 100% DuPont polyimide. The upper temperature limit is 350° C. Ferrules have precision-drilled IDs so there are no mold imperfections. The one-piece design does not require back ferrules. Vespel ferrules are fairly hard and tend to seal permanently to the column. 1/16" ferrules are used by most GCs, except Perkin-Elmer which uses 1/8" ferrules.

Please note for all ferrules:
0.4mm ID ferrules fit 0.25mm ID capillary columns
0.5mm ID ferrules fit 0.32mm ID capillary columns
0.8mm ID ferrules fit 0.53mm ID capillary columns

"Straight" ferrules are used for 1/16" OD tubing.