Optimum Nutrition Serious Mass Weight Gainer container being scooped by a person, suitable for post-workout nutrition and muscle building

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Build muscle mass and gain weight with high quality calories from protein, carbohydrates and more.
Optimum Nutrition Serious Mass, high-calorie protein powder, 12 lb container for weight gain and muscle recovery

Serious Mass

With more than 1,250 quality calories, 50g protein and over 250g carbs per shake, Serious Mass is the ideal weight gain product to help you bulk and get stronger in conjunction with your weight training.

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