Illegal Golf Clubs: Which Clubs & Criteria the USGA Bans

There are several criteria that a driver head needs to meet in order to be stamped as conforming by the USGA.

• The driver must be of a "traditional" shape. As Nike proved in 2006 and 2007, even square driver heads are allowed.
• The club must have one head and one shaft.
• Pieces that move for adjustability must stay in place during the golf swing and cannot be easily manipulated during play.
• No holes of any kind in the clubhead.
• Protrusions or depressions must not extend to the clubface.
• Heel to toe length can't exceed five inches.
• Overall driver head size can't exceed 460 cubic centimeters.
• The clubface must be rigid and smooth.
• The clubface can't produce a coefficient of restitution (COR) rating that exceeds 0.83. This refers to the trampoline effect the ball has on the clubface.
• The legal maximum length of a driver is 48 inches.

The USGA provides an updated list of conforming golf clubs every Monday. Major golf club manufacturers who need their clubs to be approved as legal by the USGA before they can be sold to the masses, so this list is a great way to find out what's in the pipeline for some of those well-known golf manufacturers.

There are significant benefits to using drivers and other golf clubs that exceed the allowed specs of the USGA.

• Drivers that go beyond the 0.83 COR rating give players significant gains in distance. This is in relation to how thin the face of the driver is and how much it acts as a trampoline for the golf ball to launch from. The COR of a driver can atually evolve the most it is used, and with pro-spec clubs already pushing the legal limits, some golf tournaments randomly test drivers to ensure this criteria is met.
• Exceeding 460 cubic centimeters in head size allows for a larger face, more surface coverage, and a non-conforming amount of forgiveness.
• Total driver length is capped at 48 inches because longer drivers have the potential to create more speed
• Holes are not allowed in the clubhead to prevent air from passing through the club, which would create an excessive amount of speed not allowed by the USGA.
• If the face of a driver is not rigid and smooth, or grooves are too deep, players would likely see gains in spin control.

Here is a list of some of the more popular golf clubs that are not legal under the rules of golf, along with where they break with USGA's criteria.

Ask you can see, there are plenty of non-confirming golf clubs for you to get your hands on if you so desire. If you're playing a casual round of golf with no handicap implications, there's no harm in trying illegal golf clubs. If you choose to play against other players in any fashion, or if you intend to record your score, any of the clubs mentioned need to stay at home.