Polypropylene sheet protectors are constructed out of standard weight material. Top loading design adequately stores documents without taking up additional binder space. The acid-free material eliminates photocopy transfer. Holders are pre-punched to fit with standard three-ring binders. Provides durable storage for 8 1/2" x 11" size documents. Visit c-lineproducts.com/environmental-attributes.html to learn about the special attributes of this product.