Polypropylene closures for aseptic liquid transfer of media, biological reagents, pure water, and chemicals. Frequently used to feed or receive from bioreactors and fermentors. Can be used with carboys or bottles that accept 53B or 83B closures. Closures 16225-228, -229, and -230 are provided with two pieces of tissue culture-grade tubing for aspiration, dispensing, and filling splash guard. TopWorks closure 21020-216 includes two 6.4mm (1/4") rubber tubes and one 9.5mm (3/8") rubber tube cured to and passing through a silicone rubber stopper/liner in an 83B closure. It is compliant with USP Class VI requirements. All closures are autoclavable.