Check the listing for details. Stopper - Polypropylene - 12/21 Socket Size - 10 Pack. Condition: New. Listed at 8.99 USD. Stopper - Polypropylene - 12/21 Socket Size - 10 Pack Lightweight and durable Polypropylene stopperFits 12/21 socketsAcid-proofAutoclavablePack of 10 stoppers 10 pack of extremely lightweight and durable polypropylene stoppers. Acid-proof and autoclavable; they are sized for a 12/21 socket. Eisco Labs proudly manufactures its own products using state-of-the-art equipment, and following the highest standards of quality control. Each product is carefully designed by a team of laboratory professionals and experienced engineers with quality and durability in mind. They are manufactured with only the highest grade, raw materials and according to international quality standards to ensure that they can withstand use in even the toughest laboratory environments. Product Details Brand Eisco Product Type Flask Stoppers MPN CH0873B Check out my other items.