Labconco Rubber Stoppers PK-100 20MM. Large size stoppers are excellent for closing valves on large open-bottom flasks or test tubes besides being used for rinsing jars and bottles. Small size stoppers are excellent for use in small open-bottom flasks and test tubes. Stoppers are made of natural rubber and are not releaded. Large size stoppers are excellent for closing valves on small test tube jars and corrosive environments. They have a long solid rounded tip and an even shape that ensures good sealing performance. Small size stoppers are excellent for use in pin-hole encapsulated filters and non-toxic pestles and insectoids . They have a long rounded tip that ensures good sealing performance. They are highly elastomeric providing soft yielding characteristics. However because of a slight imperfection some of the stoppers may show variable sealing performance. The high resiliency of the natural rubber stopper material provides good chemical and bursting strength. Therefore the stoppers should be a uniform size throughout the test tube. Sizes and color may vary. Specifications for Labconco Rubber Stoppers PK-100 20MM 7576210 : Description: RUBBER STOPPERS PK-100 20MM (Please note that the description and stock photo may not correspond to the specific model listed above) We offer only genuine Labconco products authorized for sale in the U.S. and other markets so you can be sure that you are buying authentic Laboratory Consumables with a full manufacturer's warranty in addition to our own 100percent Satisfaction Guarantee. We are your premier online distributor for Labconco Laboratory Consumables. We are an authorized supplier to all federal and state government agencies as well as to research and educational institutions and can facilitate volume orders on many types of laboratory equipment lab consumables and other products to help fulfill your specific needs. We offer Free Shipping and FREE USPS shipping to APO and FPO addresses on all orders in our store over 49. Please refer to our APO/FPO Shipping and Export Restrictions for more information on export to APO/FPO addresses. In addition to the Labconco Rubber Stoppers PK-100 20MM 7576210/ 26676-253 we carry a full complement of Laboratory Consumables as well as other product offerings from Labconco. We also carry a full line of Labconco accessories to help meet your laboratory and scientific needs. For a complete selection of Labconco Laboratory Consumables please visit our Labconco page. For more brand name Laboratory Consumables please visit our Laboratory Consumables store section. To see our complete line of lab medical industrial and scientific products please see our science and lab equipment online catalog. Labconco Rubber Stoppers PK-100 20MM 7576210