Formula: This is one of the worst nail products I have used by far. It made my nails so hard to the point any little friction against the nail surface made them break. The formula made my nails peel, split and crack and didn't offer any relief for the damage. I didn't know it contained formaldehyde until after using the product and I'm pretty sure that's what makes the nails super hard but easy to break at the same time. It's really not worth the effort to damage already weakened nails just because the product is affordable. I'm throwing the bottle out and this has been my own personal experience.