Optimum Nutrition Serious Mass is a high-calorie weight gain formula designed to support muscle growth and recovery. Each serving delivers 1,250 calories, 50g of protein, and 250g of carbohydrates to fuel intense training and promote lean mass gains. Fortified with creatine monohydrate, glutamine, and essential vitamins and minerals, this formula supports strength development and overall athletic performance. The 12LB container provides multiple servings for consistent supplementation. Ideal for athletes and fitness enthusiasts looking to increase caloric intake and maximize training results.