Golf balls having a single or dual-layered solid core are provided. In one embodiment, the golf ball has dimensions and properties that do not conform to the rules of the United States Golf Association (USGA). For example, the ball weight; ball size; ball spherical symmetry; ball initial velocity; and/or ball overall distance may fall outside of the USGA standards. The dual-layered core can have an inner core comprising a thermoplastic composition and surrounding outer core comprising a thermoset composition. In another embodiment, the dual-layered core has an inner core comprising a thermoplastic composition and outer core comprising a thermoset composition. The thermoplastic composition preferably comprises an ethylene acid copolymer ionomer and plasticizer. The thermoset composition preferably comprises polybutadiene rubber. The ball further includes a cover of at least one layer.

A golf ball for amateur golfers exhibits excellent flight characteristics when hit by the average golfer and also has a good feel at impact that is both soft and solid. The golf ball includes a core, an intermediate layer and a cover, and has coefficient of restitution and compressive deformation relationships that satisfy specific conditions.

A golf ball having a core and a cover that is formed of a resin composition which includes (A) a polyurethane or a polyurea and (B) a styrenic resin material, when dropped from a height of 3 m and made to collide with a metal plate, has velocities 200 ms before and 200 ms after contact that satisfy the condition: (incident velocity)(rebound velocity)0.80 m/s. The ball has a good controllability on approach shots without a loss in the distance achieved on shots with a driver, and thus is particularly useful to professional golfers and skilled amateurs.

A golf ball for amateur golfers is endowed with an excellent flight when hit by the average golfer whose head speed is not that high and also has a good feel at impact that is soft and solid on full shots with all golf club numbers. The golf ball, which includes a core and a cover, has a compressive deformation A under 0.2 kgf to 5 kgf loading that is 0.21 mm or less and a compressive deformation B under 5 kgf to 30 kgf loading that is from 0.73 to 0.95 mm. Also, letting D be the compressive deformation of the ball under 10 kgf to 130 kgf loading and C be the compressive deformation of the ball under 5 kgf to 60 kgf loading, the ratio D/A is from 16.0 to 20.5 and the ratio D/C is from 1.80 to 1.90.

A golf ball for amateur golfers is endowed with both an excellent flight and a good, soft feel at impact when hit by the average golfer whose head speed is not very high. The golf ball, which includes a core and a cover, has a compressive deformation A when the ball is subjected to a final load of 5 kgf from an initial load state of 0.2 kgf that is 0.18 mm or less, a compressive deformation B when the ball is subjected to a final load of 15 kgf from an initial load state of 5 kgf that is from 0.30 to 0.38 mm, a compressive deformation C when the ball is subjected to a final load of 60 kgf from an initial load state of 5 kgf that is from 1.70 to 2.03 mm and a compressive deformation D when the ball is subjected to a final load of 130 kgf from an initial load state of 10 kgf that is from 3.10 to 3.80 mm.

In a multi-piece solid golf ball having a core, a cover and an intermediate layer therebetween, the core, an intermediate layer-encased sphere and the ball have surface hardnesses which satisfy a specific relationship, and the intermediate layer and the cover have thicknesses which satisfy a specific relationship. Also, the core has a hardness profile in which the hardnesses at the core surface, core center, a position 5 mm from the core center, and a position midway between the surface and center of the core satisfy specific relationships. This golf ball, when used by mid- and high-level amateurs, enables the golfer to maintain an adequate distance on shots with a driver and achieve a good distance on iron shots, has a good spin performance on approach shots and has a good feel on impact. In addition, the ball has an excellent scuff resistance when struck with a grooved wedge.

A golf ball for amateur golfers is endowed with both an excellent flight and a good, solid feel at impact when hit by the average amateur golfer having a fast head speed. The golf ball, which includes a core and a cover, has a compressive deformation A when subjected to a final load of 5 kgf from an initial load of 0.2 kgf that is 0.18 mm or less, a compressive deformation B when subjected to a final load of 50 kgf from an initial load of 5 kgf that is from 0.85 to 1.16 mm and a compressive deformation C when subjected to a final load of 90 kgf from an initial load of 5 kgf that is from 1.90 to 2.25 mm.

A golf ball for amateur golfers is endowed with both an excellent flight and a good, soft feel at impact when hit by the average golfer whose head speed is not very high. The golf ball, which includes a core and a cover, has a compressive deformation A when subjected to a final load of 5 kgf from an initial load of 0.2 kgf that is 0.18 mm or less, a compressive deformation B when subjected to a final load of 50 kgf from an initial load of 5 kgf that is from 1.30 to 1.69 mm and a compressive deformation C when subjected to a final load of 90 kgf from an initial load of 5 kgf that is from 2.45 to 2.90 mm.

In a multi-piece solid golf ball made up of, successively, a core, an intermediate layer and a cover having numerous dimples on the surface thereof, the intermediate layer is formed of a resin material and the cover is formed of a urethane resin material, each having a specific respective Shore D hardness. The ball has a specific (intermediate layer thickness)/(core diameter) value and a specific (cover thickness)/(core diameter) value, and the core has a specific deflection and has a specific hardness profile from a center to a surface thereof. This golf ball provides an increased distance and has both a soft feel when played and a high durability to repeated impact.

A multi-piece solid golf ball having a two-layer core with an inner core layer and an outer core layer and having a cover of at least two layers including an intermediate layer and an outer layer with numerous dimples on the surface is characterized in that the hardest cover layer has a specific material hardness and the ball has a specific value obtained by subtracting the surface hardness of the overall core from the surface hardness of the hardest cover layer, a specific deflection, and a specific value obtained by subtracting the initial velocity of the inner core layer from the initial velocity of the sphere consisting of the inner core layer encased by the outer core layer. This golf ball enables relatively low head speed golfers to achieve a good distance on full shots with drivers and iron clubs and also provides a soft, comfortable feel at impact.