Best quality red rubber. Shore hardness in range 46-55. Bottom diameter moulded on top face. Resistant To Dilute Acid Alkalis And Ammonia.Bottom Diameter: 40mmTop Diameter: 49.5mmLength: 40.5mmTemperature Range: -30°C - 70°CHole Diameter: 5mmPack of 10Size 40 stoppers are ideal to use with Pyrex Heavy Wall Filter Flasks 1000mL.Please note: Extreme care must be used when inserting glass into the holes in rubber stoppers.