Any regular king size pillow case should still fit over this.
This pillow is more for stomach support and preventing rolling than for back pain. If you have back pain, this pillow may or may not help. If your back pain is related to the weight of your stomach pulling sideways at night, this pillow might offer some relief. If it's related to hip pain, this probably won't help much. However, you can also sleep with a regular pillow (or a specialty pillow) between your knees, which can provide a lot of relief for lower back pain. I like the combination of a knee pillow and a pillow like this one, because I can still easily change from one side to the other at night, but can't roll flat on my back in my sleep. Most of the large maternity body pillows on the market, which provide knee support as well as tummy/back support, are a) quite expensive, and b) very bulky.
Stomach sleepers may also be able to use a pillow like this to be able to sleep on their stomachs for a little longer. I'm just at the point where laying on my stomach isn't normally comfortable, but I can lay on this on my stomach and it supports my sides enough that there's no pressure on my baby bump.
You will need :
~ 1 king size pillow ("firm" is best)
~ a seam ripper (or a small, pointy, sharp scissors)
~ a pencil (or fabric pencil/marker)
~ something to use as a straight edge
~ straight pins
~ cotton thread
~ sewing needle or sewing machine
I used a brand new (but cheap) "firm" pillow for this project. If you have an old pillow lying around that would probably work fine, but if it's really old and lumpy the end product might not be very comfortable!