1250 calories per serving. 250g of carbohydrates 50g of protein Optimum Nutrition Serious Mass: the ULTIMATE in weight gain formulas. Serious Mass supplies you with the tools you need to pack on the pounds and develop the physique you've always wanted. Simply mix up 2 scoops with milk or water and enjoy between meals, post workouts or before bed to support gorwth of lean muscle mass. 1250 calories per serving. 250g of carbohydrates 50g of protein Optimum Nutrition Serious Mass: the ULTIMATE in weight gain formulas. Serious Mass supplies you with the tools you need to pack on the pounds and develop the physique you've always wanted. Simply mix up 2 scoops with milk or water and enjoy between meals, post workouts or before bed to support gorwth of lean muscle mass.