This Pen Loop Holder is designed to fit an A5 Format Notebook for those who may need more than one pen loop. The idea being avoiding buying a new pen loop or several for every notebook. Having more than one pen color myself that I use when Writing or shifting between pen, pencil and highlighter I like to be able to have all 3 available so I have less to carry and they are more accessible. With mine I use the LEUCHTTURM1917 pen loops which hold a standard pen securely and the pens don't get loose or shuffled around in my backpack that I carry daily.