GENERATIONS-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. When ordering this product on-line, specify which of the colours you prefer in the order comment field.