Heavy-duty reference binder features One-Touch EasyOpen rings that open, close & lock with one simple motion. Slant-D rings hold 25 percent more than standard round-ring binders. Back-mounted steel rings reduce wear & let pages lie flat. 4" capacity holds up to 775 letter-size sheets. Dual-Fold living hinge does not crack & break down. Transfer-safe polypropylene will not damage photos or your letter-size documents. SuperLife EasyOpen Locking Slant-D Ring Binder also includes exposed rivets & self-adhesive spine labels for easy identification.