Protect important documents long-term in these acid-free envelopes or use to organize everyday papers. Heavy-duty polypropylene resists tearing, repels moisture and is easy to clean. Tough, side-loading envelopes feature 1-1/4" expanding gussets that are big enough to hold more than 200 sheets of paper. Letter-size envelopes offer a hook-and-loop closure for easy opening and closing.