Our 18 x 20 4 Mil White Block Clearzip® Locking Top Bags are heavy duty plastic zipper bags that feature a white lock area for organizing, packaging, and storage items. The white block area on these 4 mil 18x20 plastic zip bags accepts rubber stamp, marker, grease pen, or ballpoint pen. 18 inch by 20 inch 4 mil white block zip locking bags are made from low density polyethylene and can be recycled. These 4 mil white block ClearZip® bags feature impressive clarity and make storage and organization simple for industrial, food service and medical industry applications. White Block Clearzip® Locking Top bags are reclosable and resealable and meet FDA/USDA requirements for use in food packaging and storage applications.