Thermo Fisher Scientific Nalgene Top Works. Flexible Systems For Nalgene Carboys and Bottles, polypropylene 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. USPVI. Material Silicone. Closure 53B. Type 2 Port. Colour Clear. Tubing I.D. 2 x 6.35mm. Sterile No. Autoclavable Yes. Pack Qty 1.