What are the hollow balls used for? What is their purpose and why do they each have a little hole drilled in them?
By their very nature, the hollow balls have less attractions to the magnets than the solid balls. They are perfect for many dent removal applications and burnishing work, especially on instruments that have thinner, soft brass such as German tubas. The small holes are threaded by the manufacturer, then painted or plated, and depending on their size, become the top of a 10′ or 100′ flag pole.