Back Wheat Bags
Many people use microwave wheat bags for the back but what's more important is to select the right shape of heat pack for your own use. The name of the heating pad doesn't really matter, whether this is the Upper Shoulder & Back Heat Pack or one of the more traditional shaped rectangular-shaped wheat bags like the Large 40cm Heat Pack or the Upper Neck & Back T-Shaped Heat Pack; they all work the same.
No matter which size or shape of back wheat bag you choose, consider are you sitting down to use the heat pack (in which case any shape will be ok to use depending on the size of the area you want to cover on your back area) or if you prefer to have a heat pack you can wear around the lower back area like the Wearable Heat Pack.