Sterilized sample-ready bags have a white write on block with a 1" bottom gusset that expands when filled, so bag stands upright.  Just tear off perforation at top, pull open with center tabs, insert sample, fold top over, and close double-wire end tabs.  Creates airtight, leak proof seal for transporting liquid, solid, or semi-solid specimens.  Clear virgin polyethylene.  Meets FDA and USDA specifications for food contact.