From the manufacture: """Unique system for housing catalog sheets in a catalog rack operates similarly to a three-ring binder. Each base holds six 1" capacity ring channels. Rings open & close without having to remove ring channel from the base platform. DublLock mechanism has three trigger positions: lock, unlock & open. Ring channels are easily snapped in place or removed. Reference angle is adjustable to either 30 degrees (low) or 45 degrees (high). Tab indexes organize material for quick reference. Heavy-gauge steel base is equipped with rubber feet & is painted in contemporary putty-colored enamel paint.""" These range from $150.00 to over $250.00.