Yes they fit the Avery Elle Storage Pockets and Yes you can trim them. I didn't order any of the wall storage because I was worried,even putting it in the studs, what the impact would be to the walls.Magnetic sheets and dies are very heavy and if you also add the stamp, I think their will be lots of boxes fall off walls and on heads. I did order one storage box today,to see if they would stack well or not on shelving or if they were even worth it. I will let yo'all know. I am impressed with the actual magnetic sheets. In the beginning the dies can pop off while you are putting dies on the other side, here was my solution. I first put all the dies I wanted on one side of the magnetic sheet. Then I laid that side down on a hard surface and proceeded to load the second side with magnets. Then I slipped them into my Avery Elle stamp storage pocket.Hope this helps. I have been looking for double sided magnet sheets for quite a while and was thrilled when these came out. Have fun!