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 attributes.c-lineproducts.com to learn more about the material attributes of this product.