Screw cap with PP (polypropylene) lined, non-slit silicone septa. Recommended for PFAS analysis in combination with silanized vials. LCMS testing showed no presence of PFAS; suitable for low-level PFAS analysis. Septa thickness 0.040", durometer 35-60 for easy piercing. Use with 1.5mL clear silanized vial 220-97331-67, or order 227-97331-94, which is a kit of 100 clear silanized vials and 100 PP/silicone septa.