Tried these clips on a sturdy, average thickness plastic covered notebook cover, a smooth hard covered 5 x 8 journal notebook, and a 5 x 8 hard denim (fabric) cover. It did not hold securely to the plastic cover; it slid off when I took the pen out of the expandable band. It was semi secure on the smooth hard cover; it needed some push to be taken off. It holds tightly and securely on the hard denim cover; I had to use a significant amount of strength to remove it. The band holds most of my pens, even those with more than average girth. This isn't the case with my very slim metal pen, the Ohto Slimline; it slid right out. I also tried a few plastic body slim pens, the Slicci and Mitsubushi 460. They held but not by much. I don't feel confident in using my coated metal-bodied pens with the fear being that it may eventually scratch them. I've experimented and placed a few of them in and out of the band with no damage done. Even with this said, I would not make it a habit of doing so nor would I use my expensive pens. So, with the right notebook it won't budge; with the right pen it holds securely. I'm satisfied with my purchase and recommend this item.
