Golf balls having foam inner core and themoplastic outer core

A golf ball, comprising:

• i) an inner core layer comprising a foamed composition, the inner core layer having a diameter in the range of about 0.100 to about 1.100 inches, a specific gravity (SGinner), and an outer surface hardness (Hinner core surface) and a center hardness (Hinner core center), the Hinner core surface being the same or less than the Hinner core center to provide a zero or negative hardness gradient;
• and
• ii) an outer core layer comprising a thermoplastic material, the outer core layer being disposed about the inner core and having a thickness in the range of about 0.100 to about 0.750 inches, a specific gravity (SGouter), and an outer surface hardness (Houter surface of OC) and an inner surface hardness (Hinner surface of OC), the Houter surface of OC being the same or less than the Hinner surface of OC to provide a zero or negative hardness gradient, wherein the SGouter, is greater than the SGinner.