they all claim to have purest forms… With their "raw material COA / lab tests", but never on a finished product.
I highly doubt any one will spend a big amount on 3rd party test to find out these are not "pure" or "clean" (without any kind of impurity or contamination free while making procedure, capsules or liquid), as all are UGlabs who sell these research chemicals.
I haven't tried their MK yet.
But I've used their 7 Alpha Ace TD, and Cardarine liquid, and they were both great.
I've also used about 5 other of their products months ago, but I'm too tired to remember which ones at the moment. LOL.
But everything I've used of theirs has been great.
I generally worry more about the reliability of a source, than form of the compound.