Reusable poly envelopes provide peace of mind when you need to store papers and documents for safe keeping. Acid-free polypropylene provides protection from dust, dirt, and unexpected spills. Smartly designed with a gusseted bottom, the envelope expands to 1-inch thick to hold more documents. Other reusable envelopes don't provide this feature, so they can only hold a very limited number of sheets. To expand the envelope, simply open it, rest it on the gusset and run your finger along the interior bottom of the envelope to widen it! It's that easy! The envelope can stand on its own as you load all your documents. The assorted translucent colors provide a convenient way to organize by color.