Activities Sports & Athletics Explaining the List of Conforming Drivers and Illegal Drivers USGA, R&A Maintain Lists of Legal (Conform to Rules) Driver Heads Share PINTEREST Email Print Some makers of 'illegal drivers' brag about it as a marketing tool; this one stamps 'nonconforming' on its sole. Courtesy of Amazon.com Sports & Athletics Golf Gear Basics History Golf Courses Famous Golfers Golf Tournaments Baseball Bicycling Billiards Bodybuilding Bowling Boxing Car Racing Cheerleading Extreme Sports Football Gymnastics Ice Hockey Martial Arts Professional Wrestling Skateboarding Skating Paintball Soccer Swimming & Diving Table Tennis Tennis Track & Field Volleyball Other Activities Learn More By Brent Kelley Brent Kelley Brent Kelley is an award-winning sports journalist and golf expert with over 30 years in print and online journalism. Learn about our Editorial Process Updated on 09/02/18 Have you ever heard golfers talking about "illegal drivers" or "non-conforming drivers"? What's that all about? The short answer: The governing bodies of golf—the USGA and R&A—set parameters that golf clubs must meet in order to be "legal" under the Rules of Golf. But just because a given driver doesn't meet those standards doesn't mean a manufacturer can't make it and sell it. It just means that such a driver doesn't conform to the Rules of Golf and, therefore, is not allowed for use in any rounds of golf played under the rules (tournament rounds and handicap rounds, for example). Some manufacturers—most of which you've probably never heard of—do make "illegal drivers" and sell them to the golfing public. But most golfers won't use such a driver because of the stigma of using a club that breaks the rules. Where to Find the Lists of Conforming Drivers The governing bodies of golf maintain lists of golf driver heads that conform to the Rules of Golf. (What many golfers think of as the non-conforming drivers list is actually called the conforming drivers list.) USGA List of Conforming Drivers R&A's Conforming Driver Search The USGA's allows golfers to download the full list, sorted either by manufacturer or product; or to conduct a search. The R&A list is browsable and searchable. They contain the same information, just presented in different ways. Any driver that appears on these lists is conforming, and, therefore, "legal" to use under the Rules of Golfer. If you cannot find your driver on these lists, that probably means the driver is non-conforming and, therefore, cannot be used in tournament rounds or other rounds of golf played by the rules. If you cannot find your driver on the list, contact one of the governing bodies to inquire. Why Drivers Are Called 'Conforming' or 'Non-Conforming' According to Appendix II, section 4c of the Rules of Golf: "The design, material and/or construction of, or any treatment to, the clubhead (which includes the club face) must not: (i) have the effect of a spring which exceeds the limit set forth in the Pendulum Test Protocol on file with the USGA/R&A, or (ii) incorporate features or technology, including, but not limited to separate springs or spring features, that have the intent of, or the effect of, unduly influencing the clubhead's spring effect, or (iii) unduly influence the movement of the ball." When golf equipment manufacturers design a new driver head, they submit it to the USGA and R&A for approval. The governing bodies run various tests to check the design and technical aspects and make sure the clubhead meets the requirements set forth in Appendix II. Those that do are added to the conforming drivers list. Those that don't? In most cases, a clubhead that fails the test is tweaked by a manufacturer until it does meet the requirements in Appendix II—until it is placed on the conforming list. At that point, the manufacturer goes into production with its new driver and the making-and-marketing process begins. Most golf shops only sell conforming drivers because most manufacturers only make and market conforming drivers. But some other companies, and, rarely, a major golf equipment brand, intentionally make non-conforming drivers. Why? Well, every golfer dreams of being able to bomb super-long drives. Those golfers who aren't bothered by the idea of playing an "illegal" club might be willing to buy a driver that promises incredible forgiveness and distance, even if that driver doesn't meet the requirements in the Rules of Golf. Most golfers won't: We don't want to be called rule-breakers—cheaters, even—by our peers. But some golfers will buy a non-conforming driver because, well, why not? They aren't playing in tournaments, they don't take the game super seriously, they just want to have fun and to play a driver that promises to help them hit it long and straight. And they aren't bothered by any looks or wisecracks their playing companions might give them. The Most Common Reasons a Driver Is Non-Conforming So what makes an "illegal driver" non-conforming? There are many possible reasons, but two are most common. When a driver is unintentionally non-conforming: Occasionally, major golf brands will, in pushing up as close to the limits as possible, unintentionally go over the limits or otherwise fail to meet the equipment requirements that are set forth in the rule book. In this case, the culprit is usually characteristic time. CT, as it is abbreviated, is a measurement of the springiness of the clubface (a measurement of the spring-like effect, in other words). A manufacturer can unintentionally exceed the limit on CT, rendering a driver head non-conforming. Typically when that happens, the manufacturer will make tweaks to the clubhead design, correct the issue and re-submit the club for approval. When a driver is intentionally non-conforming: Those off-brand or niche companies that intentionally make and market non-conforming drivers don't bother submitting them to the USGA and R&A. They build them to be "illegal," after all. How? Typically, by making the clubheads larger than the rules allow. The Rules of Golf limit driver clubhead volume to 460cc. So a company that wants to make an "illegal driver" will design a clubhead that is 500cc. Or 600cc. Or even 700cc. Huge, in other words. Way over the limits. Massive clubheads also create moment of inertia measurements far higher than are allowed by the rules.