Below is a list of Plastic Bags manufacturers from Beltsville, Maryland. Plastic bags are extremely versatile containers or carriers made of thin and often flexible polymeric films. Used to store, transport, ship and package goods in a number of industrial, commercial and residential applications, baggies such as these prove very useful as they are most often waterproof and provide some degree of protection from the elements. Commonly referred to as poly bags, the containers are constructed of processed polymer resins.