Durable polypropylene sleeves. Archival and acid free. Pass Photographic Activity Test. Open at the top. Will fit the following: Prat Screw Post Leather Binder, Prat Classic Easel Binder Prat Classic Ringbinder | Ultra clear polyester sleeves. Ideal for photography. Archival and acid free. Open on 3 sides. Will fit the following: Prat Screw Post Leather Binder, Prat Classic Easel Binder Prat Classic Ringbinder |