This 20-400 size white polypropylene screw cap has a closed top with a polypropylene/silicone/PTFE liner. The liner is ultrasonically bonded, making this cap ideal for use with biological media and other sensitive compounds. Lab packed with 48 per box. Autoclavable. Cap Material: Polypropylene. Color: White. Liner Material: Polypropylene/Silicone/PTFE. Style: Screw Cap. Top: Closed. Cap Size: 20-400. Wheaton #: 240250-01.