One of Muscletech’s many new Black Onyx supplements has now been launched at GNC. The product that’s arrived is the amino formula Amino 4XL, leaving the other Black Onyx formulas, Ultra Carnitine 3X, CLA 4X, and the recently revealed NOx Test still to come. The supplement has been introduced in just the one flavor, Fruit Punch Explosion, and one 50 serving size which is in fact 25 scoops, as a single serving is labelled as half a scoop. For now Amino 4XL is exclusively available at GNC for $64.99 a tub, or for Gold Card members it’ll be $10 less at $54.99.