These are sturdy enough to carry around with you and should work with any 3 ring binder. The pocket on the front is perfect to keep an index card for journaling the story. These envelopes are perfect for storing a project where you record the story on the index card and store your paper, pics, etc., inside until you've completed the page(s). I'm taking these and the 6x12 envelopes with me on vacation to gather brochures, travel notes, receipts, ephemera, etc.
These are not flimsy and will hold your 3D elements as well as the 12x12 papers to go with your page layouts.