I was reviewing a previous post on odd bearing failures. Someone mentioned they wanted to see an image of a hollow-ball. I wish I had a better image, but I pulled these from an old MRC (now SKF) failure catalog. This failure normally occurs in a "radial preload" failure and normally chalked up to inadequate lubrication. The idea is that their is intermittent interruption of the oil supply. I have read that some believe this is due to oxygen content or inclusions, old catalogs say the exact mechanism is not completely understood. It is known that the hollow ball is not the root cause it is just a symptom. If you have better pictures or samples I'd like to purchase them! Thanks! Search and read Bud's Take.