The Mizuno Mp-63 irons are big improvement on the rather bland MP-62 irons they replace. This time there is a real technological improvement with the Diamond Muscle design which increases the size of the sweet area about 1cm in each direction in a head that is the same size as its predecessor. The new design is based on Tour feedback where various Mizuno pros such as Luke Donald were given blind designs to test and this one came up trumps thanks to Harmonic Impact Technology (HIT) that refines sound and feel at impact. Like the MP-53 irons the MP-63 irons feature 360 degree grind to make the top line and sole appear smaller than they actually are and this works well. The set also features what Mizuno call a reverse flow where the longer irons have larger heads for a little more forgiveness. This is not particularly noticeable at address but when you hit the 3 and 4 irons it feel like you are hitting a 5 or a 6 so the principle works in practice. The grooves on the face conform to the 2010 condition of competition regulations.