Abstract: The present invention provides a drop ball sub that may be used to drop a large ball having an outer diameter larger than the inner diameter of a restriction in the wellbore such as the running tool used to run a first casing string through a second casing string. A smaller ball is used to control dropping of the large ball. The smaller ball has an outer diameter smaller than the restriction. The drop ball sub of the present invention may be used to operate any downhole tool that would benefit by receipt of a large ball. By dropping a larger ball, in one use of the invention larger valves can be controlled in the float equipment that provide a larger fluid flow path. A larger fluid flow path reduces surge pressure and enables the system to handle more debris. The present invention provides a system that preferably provides for a diverter tool above the running tool and a diverter tool below the running tool.