For short-term handling and storage of specimens: Our patented manufacturing process eliminates leaks and offers unprecedented safety. Double-track zipper is airtight and easy to close. Appropriate for use as a primary container for most specimens. Manufactured from durable 2.8-mil polyethylene that remains flexible when frozen. Custom sizes and printing available. The Series “PE” 4752-PE through 4756-PE are packaged in packs of 250 each, four packs per case. The 16″ x 16″ and 24″ x 24″ bags are packaged in quantities of 100 per case.