An ultra-lightweight sole plate assembly can include a ground engaging outer shell, a structural component, and one or more cleat members. A method of making the outer shell includes thermoforming a foil material such as polyamide. Thermoforming the foil includes applying vacuum to the foil material. Excess foil material can be trimmed from the outer shell. The structural component can be made by injecting a molding material onto the outer shell. The cleat members can be co-molded with the shell during forming of the structural component. The resulting sole plate assembly has a reduced weight with the desired traction, strength and durability.