| 摘要 |
Two-tiered dimples 8 of a golf ball have a first recessed part X and a second recessed part Y. The first recessed part X substantially forms a part of a spherical shape. The first recessed part X includes a first opening 14, a side wall curved face 16 and a flat face 18. The second recessed part Y is substantially a regular quadrangular pyramid. This second recessed part Y includes a second opening 20, a slope 22 and a bottom face 24. The second opening 20 is a regular tetragon. The first recessed part X improves aerodynamic symmetry of the golf ball. The second recessed part Y improves a dimple effect. Proportion of the number of the two-tiered dimples 8 to total number of the dimples is equal to or greater than 70%.
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