Grow! is a great way to add protein to your diet (it's our whey-only product), but if your main goal is to put on weight, you might consider Metabolic Drive Muscle Growth Formula. It contains plenty of protein (both whey and micellar casein) in addition to the high quality carbs you'll need to reach your muscle growth goals.
Here's where you can find product info on Metabolic Drive Muscle Growth Formula:
Here's where you can find product info for Grow!: