Cavity Backs and Musclebacks

Muscleback and cavityback irons by Titleist
This collection of Titleist irons includes one muscleback (far right) and three cavitybacks of varying style. Acushnet Golf

A cavity back iron is any iron in which a small to large amount of the metal across the back of the head is removed, allowing that weight to be re-positioned on the perimeter of the head, farther away from the head's center of gravity.

A muscleback iron is the term given to any iron in which there is no cavity on the back of the head, i.e., the weight is more evenly distributed across the back of the clubhead.

Many golfers believe - because we frequently hear - that mid- and high-handicappers should always play cavity back irons, while only the best golfers should play musclebacks. But is this golfer's bromide true?

Cavity back irons are better for higher-handicap golfers, but this is true because no golfer is better off playing a muscleback iron over a cavity back iron unless the golfer is skilled enough to never miss the center of the clubface.

All deep cavity back iron designs will deliver more distance from an off-center hit than will any muscleback iron, because the cavity back iron has a higher moment of inertia about the vertical axis of its center of gravity.

The Formula to Use

It's a simple formula: Higher MOI = Less Twisting of the Head from an Off-Center Hit = More Distance from Off-Center Hits. Even for the best players in the world.

By around 2007 on the PGA Tour, cavity back irons had crossed the 50-percent threshold in terms of usage; that is, a little more than half of the pros were using cavity back irons while the others use a muscleback iron design.

The reason many players use muscleback iron designs is because they are convinced that, one, they can intentionally fade or draw the ball more easily with a muscleback than a cavity back iron; and, two, they are convinced that the "feel" of impact when hitting a muscleback iron is "softer" or simply more pleasing compared to a cavity back, which increases their confidence.

(Do muscleback irons really "feel" softer than cavity backs at impact? See "How do cast irons and forged irons compare?" for that answer.)

Return to theĀ Golf Clubs FAQ index for more information.