In the game of golf, irons with the highest moment of inertia are the most forgiving. A higher moment of inertia prevents the club from twisting when the golfer hits the ball off-center. Manufacturers increase the moment of inertia and forgiveness of the club by creating a greater curvature in the face of the club.
Experienced golfers know the difference between a good hit and a bad one by the feel of the club. Hitting the ball in the club's sweet spot means there is little resistance or vibration in the shaft. Forgiving clubs have a larger sweet spot so they transfer more energy to the ball without twisting.
Forgiveness, trajectory and workability are the three primary concerns when selecting irons. Manufacturers construct clubs with a higher trajectory rating by lowering the center of gravity of the head of the club. This gives the ball more lift. High trajectory clubs are a good choice for golfers with a naturally slower swing. Workability of the club determines how well the golfer is able to direct the ball's in-flight path. The manufacturer's efforts to improve forgiveness and trajectory with the club tend to decrease its workability. These design elements make it more difficult to hit a slice or hook on purpose because of the lack of workability.