O-ring sealed cover maintains vacuum. Achieves a vacuum of better than 200 inches of water (15 inches of mercury) using the built-in, hand operated vacuum pump in the lid. Ideal for drying, preserving, storing and even shipping samples. A release button on top allows air into the plastic container to eliminate vacuum for removal of the lid. Use desiccants to keep material dry - ideal for storing chemicals, powders, sample tissues and plant sections, and for weighing samples.