Plastic sleeves feature a Corner Lock tab design that secures documents. Ideal for long-term storage, the nonstick polypropylene material is acid-free and won't lift print. Each pocket holds up to 20 insert sheets. They are three-hole punched to fit in standard three-ring binders.Plastic sleeves feature a Corner Lock tab design that secures documents. Ideal for long-term storage, the nonstick polypropylene material is acid-free and won't lift print. Each pocket holds up to 20 insert sheets. They are three-hole punched to fit in standard three-ring binders.