Our Magnetic Zinger Balls, also known as Singing Spheres or Zingers, measure 25mm, are made of magnetized Hematite, and are sold by the pair. Magnetic Zingers have amused kids and adults for hours at a time. They can be used in experiments, science projects and magic tricks. They make great (and healthy) party favors and stocking stuffers. Magnetic Zinger Balls can be used as biomagnets (healing magnets) for magnetic therapy applications. Zingers can also be used as stress balls.