These natural polypropylene plastic vials contain hinge top lids that are permanently affixed to the plastic vials and snap into place for secure closure. The 4 oz plastic vials available on this page include an E.P.A fill line at the 100 ml mark, along with 1 oz graduations on the side. These graduations and fill lines are molded within the plastic vials, intending for continual use with no graduations rubbing off or becoming inaccurate. Be sure to test these natural plastic vials with hinge top lids for a range of applications.