This is a white cardboard mailing envelope about 10 x 12. They are the best kind for decorating with the gelli plate as they have no bubble wrap inside and the cardboard takes the paint so well. When I have several things going I will grab these from my stash and just go ahead and decorated it and then file it for use later.
Here is the back side of the same envelope. This is one of the new iStencils. Just love it. I put this on top of the gelli prints using a small make up sponge dabbed in paint. You can also use a sponge roller.