Business Source Binder, Round Rings, 1-1/2" Cap, 8-1/2"x11", 4/BD, Black (BSN28552BD) Pack of 4Basic round ring binder features two triggers on the ring mechanism that provide easy access to your documents. Back mounted metal rings allow pages to lie flat. 1 1 2" capacity holds up to 350 letter size sheets. Clear pockets on the inside covers offer extra document storage with a 30 sheet capacity for each pocket. Design also features a sturdy chipboard core and exposed rivets. Three ring binder is made of polypropylene. General Information