There are five types of magnetic Half Dome Earrings: small, medium, large, small drop, and large drop. The small and medium earrings, and both categories of drop earrings, use magneticwest.com's small earring backs. The large non-drop earrings use magneticwest.com's large earring backs. You can buy extra pairs of earring backs here. If you have any questions, please call magneticwest.com's toll free customer service line at (877) 681-3913.