A convenient, economical closure for use with disposable culture tubes. Contents are maintained sterile without the need for cotton plugging. They can be removed and replaced without contamination of the contents. 38 mm size is available for use with 25600 Culture Flasks and 25630 Baffled Shake Flasks. 4 colors, as well as natural available below. Made of autoclavable polypropylene*NOTE* OTHER COLORS AVAILABLE UPON REQUEST