A mark for club head measurement in use for measuring information about a state of a club head of a golf club and provided on the golf club includes a central portion formed with a pattern having a lightness lower than the periphery thereof and a peripheral portion formed with a pattern surrounding the periphery of the central portion and having a lightness higher than the central portion.

A mark for club head measurement in use for measuring information about a state of a club head of a golf club and provided on the golf club includes a central portion formed with a pattern having a lightness lower than the periphery thereof and a peripheral portion formed with a pattern surrounding the periphery of the central portion and having a lightness higher than the central portion.

A golf club includes a club shaft having a first end, a second end, and an inner peripheral surface defining an inner space of the club shaft, and a weight piece installed on a first end side of the club shaft. The weight piece includes an insertion portion located in the inner space, and an engagement portion located outside the club shaft to engage the first end. The insertion portion includes a first portion and a second portion. The first portion has an outer diameter smaller than the first inner diameter. The second portion includes a large diameter portion having an outer diameter larger than the first inner diameter in a state before being placed in the club shaft, and at least one rigidity-lowered portion that elastically deforms the second portion so that the outer diameter of the large diameter portion becomes smaller when receiving an external force.

A golf club includes a club shaft having a first end, a second end, and an inner peripheral surface defining an inner space of the club shaft, and a weight piece installed on a first end side of the club shaft. The weight piece includes an insertion portion located in the inner space, and an engagement portion located outside the club shaft to engage the first end. The insertion portion includes a first portion and a second portion. The first portion has an outer diameter smaller than the first inner diameter. The second portion includes a large diameter portion having an outer diameter larger than the first inner diameter in a state before being placed in the club shaft, and at least one rigidity-lowered portion that elastically deforms the second portion so that the outer diameter of the large diameter portion becomes smaller when receiving an external force.

A laser mandrel system that self-centers within a hosel bore of a golf club head to allow for precision adjustment of lie and loft is disclosed herein. The mandrel includes a one-piece housing with upper and lower portions, a laser centered within the upper portion of the housing, and a plurality of o-rings extending around an exterior or interior surface of a lower portion of the housing.

A laser mandrel system that self-centers within a hosel bore of a golf club head to allow for precision adjustment of lie and loft is disclosed herein. The mandrel includes a one-piece housing with upper and lower portions, a laser centered within the upper portion of the housing, and a plurality of o-rings extending around an exterior or interior surface of a lower portion of the housing.

Methods and systems for detecting configuration states of a golf club and adjustment systems of a golf club, such as a shaft connection system. A golf club configuration detection system captures configuration data from the adjustment system of the golf club by a configuration detection device, such as a camera, a barcode scanner, or an RFID scanner. The captured configuration data is compared to reference configuration data to determine a configuration state of the adjustment system. Swing data and ball-flight data are tracked for golf-ball strikes with the golf club in the detected configuration state. Recommendations for configuration states may be generated based on the tracked data.

Methods and systems for detecting configuration states of a golf club and adjustment systems of a golf club, such as a shaft connection system. A golf club configuration detection system captures configuration data from the adjustment system of the golf club by a configuration detection device, such as a camera, a barcode scanner, or an RFID scanner. The captured configuration data is compared to reference configuration data to determine a configuration state of the adjustment system. Swing data and ball-flight data are tracked for golf-ball strikes with the golf club in the detected configuration state. Recommendations for configuration states may be generated based on the tracked data.

A golf club head is manufactured to form a cavity where the striking face of the golf club is secured to the sole and upper portion of the golf club head. A weighted composite is manipulated into a predetermined location within the cavity. The composite contains an adhesive which secures the composite within the cavity.

A ball striking device, such as a golf club, includes a head with a face having a ball-striking surface configured for striking a ball, a body connected to the face, and at least one channel in the ball-striking surface of the face. The region of highest COR response of the face is directionally enlarged toward the channel. Depending on the size, shape, and location of the channel, the face can be altered to provide greater COR response and increased energy transfer for impacts at specific locations on the face.