In a golf ball having a core and a cover of at least one layer encasing the core, the core is formed of a rubber composition which includes (a) a base rubber, (b) a co-crosslinking agent which is an ,-unsaturated carboxylic acid and/or a metal salt thereof, (c) a filler, and (d) a crosslinking initiator, and the base rubber (a) has a polybutadiene content of at least 90 wt % and a syndiotactic 1,2-polybutadiene content of from 5 to 30 wt %, the amount of filler (c) included is from 6 to 14 vol % of the rubber composition, and the ball has a specific gravity of 1.0 or more and an initial velocity of 75 m/s or less, as the result of which the golf ball maintains a low rebound, undergoes little change in properties due to changes in temperature and has an excellent durability.

The golf ball includes a core having an inner layer core and an outer layer core, a single-layered intermediate layer and cover, wherein the inner layer core is formed of a rubber composition, the intermediate layer and the cover are formed of a resin composition, and a relationship between an initial velocity of the inner layer core, an initial velocity of the entire core, an initial velocity of an intermediate layer-encased sphere, and an initial velocity of a ball satisfies the following conditions:
(initial velocity of ball)<(initial velocity of intermediate layer-encased sphere)
(initial velocity of intermediate layer-encased sphere)(initial velocity of entire core)0.70 (m/s)
(initial velocity of entire core)(initial velocity of inner layer core)0.20 (m/s) and a specific gravity of the intermediate layer and a deflection of the golf ball when compressed under a predetermined load are set within specific ranges.

A golf ball includes a core and a cover, in which a large number of dimples are formed on an outside surface of the cover, the cover is formed using an ionomer resin as a chief material, an initial velocity of the ball is set within a predetermined range, a deflection when a predetermined load is applied to the ball is set within a predetermined range, a relationship of a ratio to a lift coefficient/drag coefficient at a Reynolds number of 218,000 and a spin rate of 2,800 rpm, a lift coefficient/drag coefficient at a Reynolds number of 184,000 and a spin rate of 2,900 rpm, and a lift coefficient/drag coefficient at a Reynolds number of 158,000 and a spin rate of 3,100 rpm is specified, and a volume occupancy ratio of the dimples is set within a predetermined range.

In a golf ball having a core and a cover, the cover is formed primarily of polyurethane, the ball has a diameter of at least 42.8 mm and a weight of not more than 44.9 g and, in an impact test carried out by hitting the ball with a driver at a head speed of 40 m/s, the sum t1+t2 of the time t1 required from initial contact by the driver with the ball for deformation of the ball to reach a maximum and the time t2 required from the state of maximum ball deformation for the ball and driver to separate is not more than 660 sec. This golf ball makes it possible for golfers who have a high head speed and ordinary golfers who do not to compete without relying excessively on superiority in terms of distance.

A golf ball composition is disclosed herein that includes at least one layer formed from metal foam. The metal foam can provide lightweight, durable, and high strength design parameters for golf ball constructions in order to provide greater adaptability and customizability, among other advantages. In other aspects, the metal foam can be filled with a polymeric foam, or a liquid.