Super neodymium magnets are made of neodymium, the most powerful magnet material in the world! The largest size shown here is only the size of two dimes, but strong enough to hold a 1/4" thick pad of 3" x 3" sticky notes to a metal filing cabinet! Super Magnets are great for projects that require extreme strength in a small size; or simply to amaze friends. Due to the extreme strength these magnets are NOT FOR CHILDREN because they can pinch fingers. These large disk magnets measure 11/16" x 1/8" thick.