The most durable top-loading polypropylene document sleeve from Wilson Jones® provides reliable protection for your important papers. 5-mil thick, letter-size, acid-free, archival-safe polypropylene features a nonstick coating to prevent ink smudging. Load Orientation: Top; Sheet Protector Type: Ring Binder; Insert Size: 8 1/2 x 11; Material(s): Polypropylene.