Golf ball having a hollow center

A golf ball comprising a hollow core, the golf ball comprising:

• a spherical inner core shell layer formed from a first thermoplastic composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
• a thermoset outer core layer;
• an intermediate core layer comprising a second thermoplastic material disposed between the thermoplastic shell layer and the thermoset outer core layer;
• an inner cover layer disposed about the outer core layer, the inner cover comprising an ionomeric material and having a first hardness;
• and
• an outer cover layer disposed about the inner cover layer, the outer cover comprising a polyurea or a polyurethane and having a second hardness less than the first;
• wherein the hollow center has a diameter of about 0.15 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 0 to 5 Shore C to define a first hardness gradient, and the thermoset outer core layer has a second hardness gradient.

A golf ball comprising a hollow core, the golf ball comprising:

• a spherical inner core shell layer formed from a first thermoplastic composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
• a first thermoset outer core layer;
• a second thermoset intermediate core layer disposed between the thermoplastic shell layer and the thermoset outer core layer;
• an inner cover layer disposed about the outer core layer, the inner cover comprising an ionomeric material and having a first hardness;
• and
• an outer cover layer disposed about the inner cover layer, the outer cover comprising a polyurea or a polyurethane and having a second hardness less than the first;
• wherein the hollow center has a diameter of about 0.15 to 1.1 inches, and the shell layer has a surface hardness and an inner surface hardness, the surface hardness being greater than the inner surface hardness by about 1 to 5 Shore C to define a shallow positive hardness gradient, and the thermoset outer core layer or thermoset intermediate core layer has a second hardness gradient.