The rigid outer container or cage is usually made from galvanized tubular steel or iron. Folding IBCs don’t have a rigid outer cage and are made of very durable plastic that folds inward when empty. Flexible IBCs or bulk bags are made from various heavy duty materials such as woven polypropylene or polyethylene.IBCs are a very cost effective way to safely move a variety of products from point A to point B. http://www.steelibc.com/stainless-steel-ibc/square-stainless-steel-heating-ibc.html