Serious Mass 5.45 Kg by Optimum Nutrition is a high-calorie supplement designed for those looking to gain weight efficiently. Each serving includes 50 g of protein, 1260 calories, and 251 g of carbohydrates, along with 5 g of creatine monohydrate, 8 g of glutamine, and 24 g of essential amino acids. The main protein source comes from a blend of whey protein concentrate, calcium caseinate, and egg albumin, ensuring adequate protein intake for muscle development. Additionally, the product is fortified with a complex of 25 vitamins and minerals to support overall well-being. It is perfect for those who have difficulty gaining weight due to a fast metabolism. The product is available in a 5.45 kg container, with various flavors that have slight differences in composition. It is recommended to mix 2 full scoops (340 g) with 700 ml of water or milk. Store in a cool, dry place, away from direct sunlight. Optimum Nutrition is a brand operating in Europe from Ireland, ensuring quality and effectiveness in each product. They advise against exceeding the recommended daily dose and consulting a healthcare professional in special situations.