From Sports Illustrated Golf+ Equipment Issue (February 8, 2010)
"These are the creme de la creme of players' irons, delivering unmatched feel, workability and total ball control through the use of the cutting-edge 3D Muscle Pad." Chris Voshall, R-and-D golf engineer
By studying the vibrations and sound created at impact, Mizuno has tried to make a muscleback blade with even better sound and feel. Made from milled carbon steel, weight has been removed from non-critical areas of the MP-68 near the heel, toe, and top of the hosel, then repositioned in the back-toe area. The result, according to the company, is a sweetspot that's lower in the face along with a neutral ball flight preferred by many accomplished players. And yes, the grooves in the MP-68 irons conform with the new USGA regulations.
The MP-68 irons will be available with several different custom shafts, but come standard (3-PW) with True Temper Dynamic Gold shafts ($899) or Project X shafts ($999).