The most common type is the aerial marker ball (also known as aircraft warning spheres or visibility spheres). These are large, brightly colored balls (orange, white, or yellow) made from durable materials like fiberglass or UV-resistant plastic. Another important type is the bird flight diverter, which is specifically designed to make power lines more conspicuous to birds, reducing the risk of fatal collisions. There are also smaller reflective markers and flags used for temporary or specific applications. Some advanced markers even feature self-illuminating beacons for enhanced visibility at night or in low-light conditions.