Craft Keepers Snap Closure Envelopes. These envelopes are made from durable polypropylene, are acid- free, waterproof, and feature a secure double snap closure. Each envelope has 1-1/2in expansion capacity to hold whatever you need for your craft projects. The envelopes also fit inside the Create a Bag Crop Station. 12x12in Craft Keepers will come to you in a variety of colors. Possible colors include: clear, blue, purple. Imported.