Two-part folding skirt stoppers are designed with a double seal to keep container contents secure.As an alternative to chemical or biological experiments using standard ground glass stopper. ● Material:Silicone ● Color:White ● Turnover sleeve folds down over the container's outer neck and creates a secure seal ● Easily perforated with hypodermic needles ● Aging resistance,acid and alkali resistance ● High temperature resistance(up to 300 ℃),low temperature resistance(lowest -100 ℃) ● Excellent electrical insulation ● High stability to heat and ozone oxidation,large chemical inertness