These 3/4" C750F-M rare earth neodymium magnet cubes are marked on the north pole with a red line for ease of use. Please handle with care. a ¾” cube is a very strong magnet and can pinch hard if you get a finger or any part of your person stuck in between them. If you need a magnet that is the same size, shape, and power but without the red mark on the north pole then you want the C750F.