Playing a professional round of golf requires a complete set of golf clubs in order to accommodate all of the different challenges, obstacles and shots. This means having a set of clubs numbered two through nine, as well as a set of four wedges: pitching wedge, approach wedge, sand wedge and loft wedge. The Callaway X-18 Irons line includes all of these clubs.

### Swing Weight

A number of technical terms are used in regards to the specifications of golf clubs. The swing weight rating is a measure of the club's resistance as it is swung through the air. This is expressed by using the letters A through F as well as the numbers one through 10. This an arbitrary scale known as the Lorythm Scale.

Iron clubs in the Callaway X-18 series that are numbered two through nine all have a swing weight of C9. The pitching wedge and approach wedge have a swing weight of D0, while the sand wedge and lob wedge each have a swing weight of D2.

Iron clubs that are made with a Unifex steel shaft, however, have different swing weights. Clubs two through nine have a swing weight of D2, as do the pitching wedge and approach wedge. The sand wedge and loft wedge have a swing weight of D4.

### Loft Angle

The club's loft angle refers to the exact positioning, specifically the angle, of the golf club's head. The loft angle is determined by calculating the angle between the clubface line and the point where the golf club's face touches the ground.

The No. 2 club has a loft angle of 18 degrees, No. 3 has a loft angle of 21 degrees, No. 4 has a loft angle of 23.5 degrees, No. 5 has a loft angle of 26 degrees, No. 6 has a loft angle of 29 degrees, No. 7 has a loft angle of 33 degrees, No. 8 has a loft angle of 37 degrees and No. 9 has a loft angle of 41 degrees. The pitching wedge has a loft angle of 46 degrees, the approach wedge has a loft angle of 51 degrees, the sand wedge has a loft angle of 56 degrees and the loft wedge has a loft angle of 60 degrees.

### Lie Angle

A golf club's lie angle refers to the angle between the shaft of the club and the bottom of the golf club. The No. 2 club has a lie angle of 59.2 degrees, No. 3 has a lie angle of 59.9 degrees, No. 4 has a lie angle of 60.6, No. 5 has a lie angle of 61.3, No. 6 has a lie angle of 62, No. 7 has a lie angle of 62.5, No. 8 has a lie angle of 63.5 and No. 9 has a lie angle of 64.5.

### Length

The length is simply a total measurement of the golf club. The No. 2 club measures 39.5 inches, No. 3 measures 39 inches, No. 4 measures 38.5 inches, No. 4 measures 38 inches, No. 6 measures 37.5 inches, No. 7 measures 37 inches, No. 8 measures 36.5 inches and No. 9 measures 36 inches. The pitching wedge and approach wedge measure 35.5 inches, the sand wedge measures 35.25 inches, and the loft wedge measures 35 inches.