Flat Poly Bag 20X30 4 mil 250/CTN. These Prism Pak Brand bags are Made in the USA and are engineered to provide over three times the impact and twice the tensile strength of traditional low density polyethylene bags. The bags are made of 100% virgin Low-Density Polyethylene (LDPE) resin that meets FDA/USDA specifications. Prism Pak Brand bags can hold everything from small parts to all types of food items. They can also be heat-sealed to provide security and/or retain freshness. Prism Pak Brand bags are in stock and usually ship within 24 hours.