These Envelopes do not expand. Envelopes comfortably hold 25-30 sheets of 12x12 cardstock/patterned paper and 12x12 sticker sheets, depending on the paper thickness.
Some of our favorite ways to use the Extra Large flat storage envelopes:
Store all the 12x12 papers from a single collection together
Store and organize 12x12 sticker sheets
Keep an in-progress scrapbook or card project all in one place
Store the papers from a 12x12 paper pad together in one place
Keep 12x12 Chipboard sticker sheets flat