Geyer's graph magnets are great for the math classroom. There are a variety of options to choose from. Dry erase graph or grid magnets will stay on any metal or magnetic surface! The magnet measures 23" wide x 24" high and is ideal for demonstrations or at-the-board work. Easy to store when not in use. For use with dry erase markers. These are great for the math classroom and can be used for demonstration purposes or can be used for small group activities. Certainly an effective tool!