The SPME cap is a great addition for any current SPME user. These polytetrafluoroethylene (PTFE) caps are chemically inert have been shown to greatly improve the on-fiber stability of extracted VOC's between sampling and introduction onto GC/MS instrumentation. In-fact not only are extracted analytes stabilized, proper capping of your SPME fiber can prevent fiber contamination from environmental or laboratory air. These are truly a must have for field sampling and laboratory applications alike.