Description_x000D_ General description_x000D_ Silicone rubber rings with sealed-in silicone sponge filters._x000D_ These silicone sponge closures are ideal when working with aerobic cultures; they permit an efficient exchange of gases. They also cut losses due to evaporation in half in comparison to cotton plugs, thus minimizing changes in pH values. They can be dry heat sterilized repeatedly at 180°C and are easy to clean and maintain (reusable)._x000D_ Compatibility_x000D_ For use with 25, 50 mL Erlenmeyer and 25-125 mL DeLong flasks.