Generally speaking, the fridge magnets you buy from gift or souvenir shops will have a flexible rubber or ferrite magnet on the back. Both types of magnets are great value for money while not as strong as neodymium magnets, they are more than strong enough to hold a lightweight item to a fridge. Both are flexible rubber and ferrite magnets are available with self-adhesive on one side and are great for making your own rubber fridge magnets.