Designing "game improvement" in an iron used to be a matter of give and take. Give distance, take away control; give forgiveness, take away feel. But new materials and methods provide engineers more freedom. It seems today's give doesn't take as much as it used to.\n"Modern technology isn't as overt," says Alan Hocknell, Callaway's head of research and development. "You can show up to the course with irons that look classic and beautiful, and there's still so much technology packed under the hood."\nGame-improvement irons are primarily designed to launch the ball higher and improve ball speed on off-center hits. This is achieved by changing the way weight is distributed in the clubhead.\n"The main limitation with designing irons is weight," says Michael Vrska, Wilson Staff's global director of research and development. "All of our head designs weigh about the same, but the thinner we can make a face, the more we can move that weight to the perimeter of the clubhead, which automatically increases ball speed and forgiveness."\nHowever, the benefits of a thinner face don't occur in a vacuum. Players still want an iron that feels good. "Feel always makes us sweat," says Benoit Vincent, chief technical officer for TaylorMade. "It's one of our biggest challenges as we start to redefine the structure of an iron."\nUnderstanding what happens to the club at impact helps designers produce the desired feel. "We study how the head vibrates," says David Llewellyn, golf-club research and development manager at Mizuno. "By strategically making areas of the head more rigid or less rigid, we can get those frequencies that we're looking for."\nThat knowledge can make feel more of a given, leaving the degree of forgiveness tied to things like clubface size and offset (the amount the clubhead is set behind the shaft). Better players, for example, might want a compact head with little offset without sacrificing forgiveness on off-center hits. Other players who struggle with a slice might need more offset and a larger clubhead. But even those irons aren't as "oversize" as they used to be.\n"Game-improvement irons today defy classification," Hocknell says. "They're distance irons that don't look like distance irons."