Business Source - BSN28552 Basic 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.