Quality has now become synonymous to clean steel grades used for the production of bearings. Issues of macro and micro inclusions that reduce the mechanical properties of steel is no longer tolerated by customers who place high demands on the performance of materials they use each day in production. This book focuses on the detection and evaluation of macro inclusions in bearing steels. It concludes that the macro inclusions from casting powder and runner/trumpet refractory constitutes the highest percentages among all the sources of macro inclusions in the casting system, this may however vary from system to system. This book therefore provides more insight into inclusions and how materials in casting systems interact with the molten steel.