Tough and big, these side-loading envelopes boast gussets that expand to 1 1/4". Acid-free, archival quality envelopes are perfect for long term storage of important documents. Heavy-duty polypropylene resists tears and repels moisture. Hook and loop closure. Letter size. Tough and big, these side-loading envelopes boast gussets that expand to 1 1/4". Acid-free, archival quality envelopes are perfect for long term storage of important documents. Heavy-duty polypropylene resists tears and repels moisture. Hook and loop closure. Letter size.