Optimum Nutrition Serious Mass is a high-calorie weight gainer powder formulated for those looking to support their muscle gain and metabolism. With a focus on gym training, weightlifting, and fitness, this product is designed for men's health and athletic performance. Containing a blend of active ingredients, including protein, this product is ideal for those seeking to supplement their diet for increased muscle mass and strength. Ideal for athletes and bodybuilders, Optimum Nutrition Serious Mass provides the necessary nutrients to support intense workouts and training routines.