I brought the Vitamin Shoppe brand and I think its pretty good. After I brought it I heard of some better ones that can be brought online but I am going to finish this before buying anything else. Do a search and you will find some brands people wrote reviews about
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I think you will find everyone has their own preference brand. Just make sure its pure as far as possible.
My brand isnt sold in the USA but I am considering changing to the range sold on www.a1-msm.com. Its sold internationally. The website also tells you how to test your MSM to check whether its pure. Worth a look.