I found Nail Envy made my nails flakey, it's okay as a base or top coat occassionally, but not as the prep that they recommend. (I'm sure it's a ploy to make you use far more product than you usually would). I've had the best nail strengthening results with the Pro Strong pro tough. I don't use it as directed, but keep it by my computer keyboard so when I have a spare mo (and I remember!) I paint it on. As someone who has stopped biting their nails in recent years, the Pro Strong really gave my nails the strength they needed to grow.