m-stak and animal stak are different products.
i dont know what's in m-stak because it just looks like a bunch of underdosed junk, but i've never used it, so who knows,
but animal stak (formerly animal stak 2 because original animal stak was a bunch of andro prohormones stacked) is a good test booster, and one of my favorites.
stack it with an ai like topical formestane for a big increase in free & total test.
people like m-stak, but i've just never had an intrest in using it, looking at it again, it does look like it could be benificial to stack the two (m-stak + stak2), but I would still say to add in an ai to take it to an whole nother level.