Abstract: In a head, a center vertical cross section passing through a face center satisfies the following (a) and (b): (a) when a boundary point between an inner surface of a crown portion and an inner surface of a face portion is defined as a CF inner surface boundary point, a curvature radius of a head inner surface at the CF inner surface boundary point is 6.0 mm or greater and 10.0 mm or less, and the head thickness at the CF inner surface boundary point is 2.0 mm or greater; and (b) when a spot located 10 mm apart from the CF inner surface boundary point toward the crown side is defined as a spot C10, the head thickness reduces gradually from the CF inner surface boundary point to the spot C10, and the head thickness at the spot C10 is 1.0 mm or less.

Abstract: A head includes a body member that has an opening, and a face member that includes a striking face and closes the opening. The face member includes a face portion that forms the striking face, and a peripheral portion that extends from a peripheral edge of the face portion toward a back side. The peripheral portion of the face member is welded to the body member. A weld bead that juts from the inner surface of the head is formed at a boundary position between the peripheral portion and the body member. A wall thickness at a face-side end point of the weld bead is greater than a wall thickness at a body-side end point of the weld bead. The peripheral portion has a length of less than or equal to 6 mm.

Abstract: In a head, a center vertical cross section passing through a face center satisfies the following (a) and (b): (a) when a boundary point between an inner surface of a crown portion and an inner surface of a face portion is defined as a CF inner surface boundary point, a curvature radius of a head inner surface at the CF inner surface boundary point is 6.0 mm or greater and 10.0 mm or less, and the head thickness at the CF inner surface boundary point is 2.0 mm or greater; and (b) when a spot located 10 mm apart from the CF inner surface boundary point toward the crown side is defined as a spot C10, the head thickness reduces gradually from the CF inner surface boundary point to the spot C10, and the head thickness at the spot C10 is 1.0 mm or less.

Abstract: Provided is an impact point estimation apparatus that is capable of estimating, easily and with high accuracy, an impact point on a face surface of a golf club head at the time of a golf swing. The impact point estimation apparatus includes an acquisition part configured to acquire time-series sensor data that is output from at least one of an angular velocity sensor and an acceleration sensor attached to at least one of a grip and a shaft of a golf club and an estimation part configured to estimate the impact point, according to a shaft characteristic which is a characteristic of the shaft, based on the sensor data.

Abstract: A golf club set includes a plurality of golf clubs 1 having different loft angles. The golf clubs 1 include at least one 1st golf club 1A having a loft angle of less than 34 degrees, and at least one 2nd golf club 1B having a loft angle of not less than 34 degrees. Each of the at least one 1st golf club 1A and the at least one 2nd golf club 1B comprises a clubface 3 provided with a plurality of face grooves 8 having a depth. The depth of the face grooves 8 of the at least one 2nd golf club 1B is larger than the depth of the face grooves 8 of the at least one 1st golf club 1A.

Abstract: A golf club set includes a plurality of golf clubs 1 having different loft angles. The golf clubs 1 include at least one 1st golf club 1A having a loft angle of less than 34 degrees, and at least one 2nd golf club 1B having a loft angle of not less than 34 degrees. Each of the at least one 1st golf club 1A and the at least one 2nd golf club 1B comprises a clubface 3 provided with a plurality of face grooves 8 having a depth. The depth of the face grooves 8 of the at least one 2nd golf club 1B is larger than the depth of the face grooves 8 of the at least one 1st golf club 1A.

Abstract: Provided is a GUI display device that is able to explain the movement for holding the wrist cock and the movement for releasing the wrist cock during a golf swing visually in easily understandable manner. The GUI display device includes a display control part. The display control part simultaneously displays, on the GUI screen, a first graphic G1(i) representing a strength with which a wrist cock is held at an i-th timing during a swing motion of a golf club, and a second graphic G2(i) representing the strength with which the wrist cock is released at the i-th timing, where i=1, 2, . . . , N (N being an integer of 2 or more).

Abstract: Provided is a GUI display device that is able to explain the movement for holding the wrist cock and the movement for releasing the wrist cock during a golf swing visually in easily understandable manner. The GUI display device includes a display control part. The display control part simultaneously displays, on the GUI screen, a first graphic G1(i) representing a strength with which a wrist cock is held at an i-th timing during a swing motion of a golf club, and a second graphic G2(i) representing the strength with which the wrist cock is released at the i-th timing, where i=1, 2, . . . , N (N being an integer of 2 or more).

Abstract: Provided is an impact point estimation apparatus that is capable of estimating, easily and with high accuracy, an impact point on a face surface of a golf club head at the time of a golf swing. The impact point estimation apparatus includes an acquisition part configured to acquire time-series sensor data that is output from at least one of an angular velocity sensor and an acceleration sensor attached to at least one of a grip and a shaft of a golf club and an estimation part configured to estimate the impact point, according to a shaft characteristic which is a characteristic of the shaft, based on the sensor data.