Photo taken from google images
Now the downside ... this will not prevent nail stains. A good base coat will help with staining, but this does not. Whatever polish you use, if it bleeds, it will bleed right onto your nails. The other issue is that it does leave ridges if you are not careful. The product is slightly thick, so there is unevenness and therefore leaving very minor ridges on your nail polish bed.
So it's a give and take you see. If you want strong nails, this works, but you can't have it all I suppose. Or maybe you can, and I just haven't found the product that does so.
It comes in a 4ml and 10ml bottle. I have the 4ml and I believe it will last me about a month or maybe even 6 weeks. The prices vary depending on which online shop you purchase it from, but I would definitely get a sample before investing on the full size.