I accidentally lost one of my earring backs when I tried to remove my diamond studs at home.  I was devastated and had been searching the carpeted floor inch by inch for days, hoping it would just show up one day.  After one week of search, I decided to give up and started looking for a replacement back.  It would cost $20 for a 14K screw back earring back but I wasn't sure if it would fit my threaded post.  I came across this listing and was very skeptical about this product, especially at this price tag.  However, I convinced myself to splurge based on the positive feedback.  Well, I wasn't disappointed.  They fit my threaded post and seem to put my diamond studs a bit upward, which look better IMO.  Also, I can pull the back closer to the end of the post so they wouldn't poke me when I sleep.  There is a learning curve to use this product.  Because I use it on threaded post, I wasn't really sure if I could use force to insert or pull out of the post.  However, after using it for a few days, I'm more comfortable with it now.  I only hope that I won't lose the back ever again or it would cost me more to replace it.