In the U.K. these polymers are better known by the word Nylon but as this is a registered trademark in certain European countries, it is likely that the word Polyamide ( Relyon) will be used in the future. These compounds are formed from the polymerization of the reaction product of an acids and an amine. Hitherto, they have been known by suffixing the word Nylon with a number, e.g. Nylon 6, Nylon 66, Nylon 10, 11, 12 etc. Polyamide ( Relyon) 66 is formed by the combination of hexamethylenediamine and adipic acid. Polyamide ( Relyon) 6 is formed by the polymerization of caprolactam. All the Polyamide ( Relyon)s and suture materials are produced by an extrusion process, the size of the orifice on the extruder head determining the size of the filament. The bulk of the material used in surgery is produced in the form of monofilament. Its main use is in skin suturing although it is sometimes used internally. Polyamide ( Relyon) mesh finds a use in hernia repair. Finer filament of Polyamide ( Relyon) is braided together to form braided nylon on non- absorbable surgical sutures. Monofilament Polyamide ( Relyon) is normally colored with distinctive non-toxic dyestuffs or pigments in order to improve its visibility. It may be sterilized by autoclaving, by ethylene oxide or by radiation treatment, but is incompatible with phenol and its homologues and other phenolic substances. The knotting of Polyamide ( Relyon) requires a special knot.