I have been using two supplements, the Vita Flex E & Se and the Mag5000. The E & Se isn't a powder, its more like a ground meal. The Mag5000 is pelleted. I had Smarkpak send me a few samples of their E-Se-Mag to try since I thought it would be easier just to feed one supplement with all ingredients. My hoover of a horse wasn't thrilled with the E-Se-Mag and picked and poked at his feed and normally he's not picky about anything. He eats both of the others with gusto. Unfortunately SmarkPak doesn't carry the Vita Flex E & Se but my local Southern States does. I think using both of those sups together gives you a little higher Mag content, 5000 as opposed to 3000 of E-Se-Mag.