I have lots of folders and notebooks where it would be so handy to have a writing implement nearby and these clips do that job perfectly. They clip on and the pen slides into the ring. It can go on the inside of a spiral bound book for instance, so the pen is within the spirals and can't be knocked off
This seemed what we needed and worked fine. It has just expired so I looked up when I bought it and it lasted almost exactly 1 year with pretty much daily use in our porch. I suppose I expected it to last a bit longer really.