Strong Magnets: strong enough to hold all kinds of poster, picture, photo and artwork with flat surface Changeable & Resuable: no tape and no damage. You can change up the poster or kids canvas artwork from time to time as you like Wide Compatibility: not only a 21cm poster frame, but also can be used for a poster of less or more than 21cm in width Easy Operation: just place your poster into correct position, and hang it up with a hide rope Kindly Note: a big thickness of your poster may affect the magnets, so it might not be for thick poster or canvas