• Produces a leak resistant seal that can be punctured as often as needed to allow through-cap sampling. • Disposable santoprene closures can be used on all glass and plastic tubes with an internal diameter of 12 to 16 mm. • Easily applied and removed with one hand. • Protects samples from evaporation and contamination. • Withstands agitation in a test tube vortex mixer. • Can be used in the refrigerator, freezer or at room temperature.