These 18" x 18" anti-static shielding ESD Zipper Locking bags are made from a multi-layer 3 mil laminated film and insure a continuous static shield when the zipper closure is locked together. This layer functions as a barrier to E.S.D which allows a charge to move around and not through the bag. The inner layer of this 3 Mil bag provides static dissipative protection for the metal layer and also strengthens seal. The outer layer of this 3 mil bag is a non-static generating layer that resists abrasion and puncture.