This particular egg crate was made to be used under sleeping bags during camping trips, since it has a stiffer rubberized side on it. I like that because it makes the foam rigid so I can pick pieces of it up and carry it around without having it collapse.
Of course, I couldn't find any more of it when I needed it, so I bought a different style online. You can get egg crate foam in different depths, but I find that 1 1/2-2" is enough. If it's deeper than that it's hard to use because it's too cupped.
I decided that it' so useful, I would add it to my shop. Click here to get yours: Egg crate foam
Kara Buntin owns A Cake To Remember LLC in Richmond VA, and cake supplies online at www.acaketoremember.com and www.acaketoremember.etsy.com