Business Source - BSN74449 Durable, top-loading sheet protectors hold letter-size inserts without punching. Printed materials do not stick or lift off this specially formulated, polypropylene material. Design features a reinforced strip at binding edge, 3.3 mil thickness and three-hole punched sides. Die-cut corners on ring side allow heavyweight pages to turn freely. Oversized ring binders and indexes are sold separately.