Abstract: The present invention provides an apparatus and system for mixing castable polyurethanes for dispensing into a golf ball mold for application to a golf ball sub-assembly. The apparatus comprises a mixing block for merging together at least two polyurethane components, then a temperature control chamber to remove excess heat that is produced by the exothermic reaction resulting from the mixing of the urethane components. The mixing of the components is by passing the components through a tortuous mixing path created by a disposable static mixer element. The mixed components are dispensed into the golf ball mold by a multiple lead nozzle assembly.