Perfect for science and engineering exploration and investigations, each marble features a red north pole and a blue south pole. Simply give them a roll to see opposite poles roll toward each other and attract... or make poles repel. Add to the learning by incorporating a magnet wand or another magnet in a different format (not included). Drag a string of marbles or make them spin, wiggle, or jump. Safe, low power magnet marbles measure .63" D. Approved for safe use for ages 4+, Enough marbles for multiple small groups or science stations. 100 per package.