MUTANT MASS EXTREME 2500 was made for extreme hard gainers who can't gain enough mass no matter how much they eat or how hard they train. Those with an extremely fast metabolism and busy on-the-run lifestyle need extra calories but have difficulty eating enough to gain size. When added to your diet and training, nothing packs on mass like MUTANT MASS EXTREME 2500. Drink anytime but we prefer one shake post-workout and another in between meals or before bed to fuel your body with an extra 2100-2500 calories per day!