These work very well!
As a life long nail biter, I quit that habit when the Covid-19 came along.  My nails are very weak and thin…mostly due to poor thyroid function.  So I used the emery boards, but my nails would snag and pull off.  I read online that glass files were superior.  So I gambled and purchased these. I keep one in the kitchen, one beside my bed, one in my car, and one in the bathrooms.  Keep them handy anytime I see a snag beginning.  My nails are a bit longer now.  No more acrylic nails for me.
Rating: 5 stars