Description: *9 different diameters, suitable for different sizes of experimental filtration apparatus. * Made of high-quality durable vulcanized rubber, good elasticity, smooth surface and wear-resisting. *Used for filtration assemblies, together with a Buchner funnel and a Buchner flask for filtration. *Can be used singly or nested with adjacent sizes, reduce the risks associated with insertion and removal of glass stems through these rubber stoppers. Guarantee: *Your 100% satisfaction is our final goal, if you have any problem about the item, just feel free to contact us. *Click Add To Cart today to get this wonderful accessory for your science project. *100% MONEY BACK GUARANTEE - We want you to be 100% Satisfied with your purchase. Absolutely no risk. Give our product a try by ordering today.