Never lose your pen again! This is exactly what I wanted! A pen case that attaches to your planner Pen case for attaching to your planner Attaches perfectly with rubber and Velcro. For those times when: Your pen disappears in your bag, It fell out of your planner even though you put it in there, This solves those problems. Holds 3-4 pens. Compatible with planner sizes from approximately 19 to 23 centimeters.