Golf club assembly and golf club with aerodynamic features

A golf club head for a driver, the golf club head comprising:

• a body member having a ball striking face, a crown, a toe, a heel, a sole, a back and a hosel region located at an intersection of the ball striking face, the heel, the crown and the sole;
• the sole including a diffuser that extends from adjacent the hosel region toward the toe, wherein the diffuser is recessed within the sole, the diffuser having a width measured from a first side of the diffuser adjacent to the ball striking face along a perpendicular to a centerline of the diffuser to a second side of the diffuser nearest the back of the body, and a depth measured from an imaginary surface that extends from the portion of the sole surface adjacent the first side to the portion of the sole adjacent the second side to a bottom surface of the diffuser;
• wherein the width of the diffuser increases and the depth of the diffuser decreases as the distance from the hosel region increases;
• wherein the diffuser includes a vane that projects from a bottom surface of the diffuser and is centered between the first side and the second side of the diffuser, the vane extending over a majority of the sole.