Solid rubber stopper dimensions: Diameter 20mm - 15mm, Length 25mm. The thickest rubber stopper is 20mm. The thinnest rubber stopper is 15mm. Measurements are approximate. Set of 10! Although new and unused, there is some slight orange discoloration due to long-term storage, but it is usable. Can be used to seal and close test tubes, containers, and flasks to prevent leakage.