For NALGENE carboys and bottles with PP screw closures, platinum-cured silicone inserts. Flexible silicone top works systems include solid, 2-port and 3-port versions. Platinum-cured silicone tubing is fused through stopper to form one-piece closure system. Permits aseptic liquid transfer from most NALGENE bottles and carboys. Autoclavable, leakproof, class USPVI. For NALGENE carboys and bottles with PP screw closures, platinum-cured silicone inserts. Flexible silicone top works systems include solid, 2-port and 3-port versions. Platinum-cured silicone tubing is fused through stopper to form one-piece closure system. Permits aseptic liquid transfer from most NALGENE bottles and carboys. Autoclavable, leakproof, class USPVI.