Extra-tough case bound binders are built to stand up to the most abusive use conditions, making them almost indestructible. Vinyl construction with heavyweight inner chipboard stands up to the toughest use. Heavy-duty ring mechanisms hold contents tightly in place. No ordinary case bound ring binder, this heavyweight storage giant holds its shape even when subjected to rough, constant use. Locking round rings secure sheets without gaps. Metal-hinge construction for extra-strength durability.