Poly Back is the most economical and most common automotive carpet option. This is the same material that all discount carpet retailers offer. Poly Backing is a more flexible, plastic type backing that is easy to cut and fold for shipping. Mass Back is a rigid rubber backing that is the common original equipment (OE) for many late model cars. Carpets made with Mass Back are heavier and more difficult to ship. Click here to read more about the automotive carpet backing.