I have the bigger one. I generally only use my Olfa frosted 6 X 24" ruler. I found that the gripper wouldn't stay attached to my ruler. I cleaned the ruler, cleaned the suction cups, moistened the suction cups and applied pressure to the gripper before locking it onto my ruler. It would still come off! I may have needed a smaller one because I found that the ends were generally covering the lines on the my ruler that I wanted to use for cutting and measuring. I took it off and I thought I would store it on the side of my sewing cabinet. I couldn't get it to stay stuck there either!!!! I didn't pay alot for it as I found it on a clearance table at a LQS.