A golf club head includes a top portion, a sole portion opposite the top portion, and a striking face configured to impact a golf ball. The striking face includes a face center and a variable thickness distribution such that the club head exhibits an Expected COR value of not less than 0.810, the Expected COR value being determined based on the following relationship:

[00001]$\mathrm{Expected}.Math..Math.\mathrm{COR}=\underset{i=1}{\overset{n}{.Math.}}.Math.\underset{j=1}{\overset{m}{.Math.}}.Math.p_{\mathrm{ij}}*c_{\mathrm{ij}}$

The variable c.sub.ij corresponds to an average COR value associated with bin i, j, and the variable p.sub.ij corresponds to a bin-specific impact probability value. And the club head exhibits a characteristic time no greater than 257 microseconds.

A golf club head having a striking face configured to impact a golf ball comprises the striking face comprising an effective striking area, the effective striking area having an expected COR value, defined by the following expression, not less than 0.810, $\mathrm{Expected}\mathrm{COR}=\underset{i=1}{\overset{n}{.Math.}}\underset{j=1}{\overset{m}{.Math.}}{p}_{\mathrm{ij}}*c_{\mathrm{ij}}$
wherein p.sub.ij is an impact probability at location or region (i, j) within the effective striking area, and c.sub.ij is a COR value of the location or region (i, j).

A golf club comprising a golf club head having a face wall, an inertial motion unit (IMU) positioned within the body, and a transceiver in communication with the IMU, a shaft attached to the golf club head, and a grip attached to the shaft is disclosed herein. The IMU identifies an impact location with a golf ball.

Provided is a weight pattern determination apparatus for determining, in a golf club having a head capable of mounting one or more weights in a plurality of mounting patterns, the mounting pattern suited to a golfer. The apparatus has an impact point specification unit and a pattern determination unit. The impact point specification unit specifies an impact point distribution of the golfer. The pattern determination unit determines a recommended pattern which is the mounting pattern that approximates a sweet area of the golf club to the impact point distribution. According to the first aspect of the present invention, the impact point distribution of the golfer is specified, and a mounting pattern is determined based on this impact point distribution.

The invention is a device attachable to a golf club which provides feedback, when the ball is struck on a sub-optimal area of the clubface, or at a suboptimal angle. The device is shaped to cover certain areas of the clubface, except the desired striking zone, such that the golf ball strikes the device during an impact resulting from a golf swing with sub-optimal swing path, attack angle or club face angle. The device provides physical and audible feedback, during impact of a golf swing, due to the differing feel and sound generated when the ball impacts the device, rather than the optimal area of the clubface. The device provides visual feedback, as due to the convex shape of the device, a differing golf ball flight is achieved when the golf ball impacts the device rather than the optimal area of the clubface.

A golf club set includes at least one first golf club whose loft angle is not less than 46 degrees and less than 56 degrees, and at least one second golf club whose loft angle is not less than 56 degrees and less than 60 degrees. The first and second golf clubs each comprise a face provided with score lines each formed by a groove having a groove bottom and a pair of opposite grooves walls which are inclined at an inclination angle with respect to a normal direction to the face so that the groove width between the opposite grooves walls is increased from the groove bottom toward the face. The inclination angle of the groove walls of the score lines of the first golf club is in the range from 28 to 42 degrees. The inclination angle of the groove walls of the score lines of the second golf club is in the range from 23 to 37 degrees and smaller than that of the first golf club.

A method of manufacturing a golf club head includes: (a) providing a model of a golf club head, the model including a striking face portion and a first plurality of structural attributes; (b) generating first data comprising relationship information between locations about the striking face and predicted coefficient of restitution or characteristic time values based on modeled golf ball impact; (c) providing second data comprising relationship information between generalized striking face position and impact probability; (d) calculating a first expected overall performance value based on the first data and the second data; (e) modifying the first plurality of structural attributes based on the first expected overall performance value, resulting in a second plurality of structural attributes different from the first plurality of structural attributes; and (f) forming a golf club head having club head structural attributes corresponding to the second plurality of structural attributes of the model.

A golf club head having a striking face configured to impact a golf ball comprises the striking face comprising an effective striking area, the effective striking area having an expected COR value, defined by the following expression, not less than 0.810,

[00001]$\mathrm{Expected}.Math..Math.\mathrm{COR}=\underset{i=1}{\overset{n}{.Math.}}.Math.\underset{j=1}{\overset{m}{.Math.}}.Math.p_{\mathrm{ij}}*c_{\mathrm{ij}}$

wherein p.sub.ij is an impact probability at location or region (i, j) within the effective striking area, and c.sub.ij is a COR value of the location or region (i, j).

A golf tee has a contact alert material encapsulated therein. The golf tee includes a top portion with top, side and bottom walls fixedly attached to a shaft that terminates into a point appointed to be inserted into a ground surface. A cavity is formed between the top, side and bottom walls of the top portion. A contact alert material is encapsulated within the cavity and is composed of a combustible material that generates a spark on impact. The contact alert material is appointed to generate the spark during a golf swing when a golf club strikes the ball and the side walls. The alert is provided immediately as instantaneous feedback during the golf swing adapted to thereby improve muscle memory required to reliably replicate a proper golf swing.

The present disclosure includes systems, devices, and methods for initiating application of a substance to a surface of a golf club. The substance configured to provide a golfer with feedback on which portion of their golf club they strike a golf ball with. For example, an apparatus may include a first component configured to receive a golf club and an actuator configured to initiate application of a substance to a surface of the golf club configured to contact a golf ball. Other aspects and features are also claimed and described.