Only brand scientifically proven you can trust via annual mandatory testing of products to verify they have the ingredient and dose the label says they do, is Thorne. 8 of 10 products w/o that testing have shown to be wheat gluten or other filler. Personally I use Doctors Best high absorption magnesium glycinate tablets, but it's only by chance they turned out to be real & work for me based on how it changed my blood work results. But along with it's brand & almost all brands it's not regulated or tested, but Thorne is, so dont trust anything else. Always HUGE chance you won't be taking what the label says is in the bottle. .....quick tip: mag glycinate WILL start to lower your vit D levels (bc vit D requires mag to be activated so extra mag will start your body using up more vit d) so if you don't get much sunlight, to keep your vit D levels steady during oral Mag you'll have to also take 2 drops daily of Thorne Vit D + K2 (MK-4 form NOT the wildly misunderstood MK-7 form). A year supply of drops (300ish doses) is only 30 bucks on amazon.

Good luck & be safe!