you can make your own magnesium oil for way cheaper.you need nigari(Magnesium chloride)
its used to make tofu, all magnesium oil is is nigari mixed with water, ive been making it for afew months now and my muscle cramps and muscle twitches are completly gone.you might be able to find nigari at asian food stores where they keep there tofu making supplies but i ordered mine online at http://www.herbalhut.com,im
sure there are other vendors online aswell just google "tofu making supplies nigari". good luck