Best quality red rubber. Shore hardness in range 46-55. Bottom diameter moulded on top face. Resistant to dilute acids alkalis and ammonia.Bottom Diameter: 29mmTop Diameter: 33mmLength: 32mmTemperature Range: -30°C - 70°CPack of 10Size 29 stoppers are ideal to use with Pyrex HD NM Conical Flasks 500mL Pyrex Flat/Round Bottom NN Flasks 250-500mL and Pyrex Conical WN Flasks 100mL.