The Callaway ERC II was a forged titanium driver that Callaway knowingly built to exceed the USGA's limit on "spring-like effect," then sold in the United States anyway. Announced in October 2000 at $625, it could not be used in USGA-governed play, yet Arnold Palmer endorsed it. The fight it started helped shape the 0.830 COR limit every driver is built to today.
What was the USGA rule the ERC II broke?
In 1998 the USGA adopted a test for the "trampoline" or spring-like effect of a driver face, measured as the coefficient of restitution (COR). The limit was 0.830. A thinner, more flexible face returns more energy to the ball, and the USGA estimated each point of COR is worth about two yards. In 2001 the Christian Science Monitor reported that the hottest non-conforming drivers reached about 0.90, worth 10 to 15 yards.
The R&A, which writes the rules for most of the world outside the United States and Mexico, did not adopt that limit at first. That split is what made the ERC II story possible.
What was the ERC II?
Callaway released the ERC II on October 24, 2000. Per Callaway's own announcement, it had a forged titanium face with the company's Variable Face Thickness design, thickest in the center and thinnest at the edges, a head about 11 percent larger than the original ERC Forged Titanium driver, and System 50 graphite shafts in lofts from 8 to 12 degrees. Suggested retail was $625. It was Callaway's first non-conforming driver sold to U.S. golfers, and the company offered the Hawk Eye VFT driver as its conforming option for tournament play.
Ely Callaway said of it, "It is a much more forgiving driver than any we have ever made."
Why did Callaway sell a club that wasn't legal?
Ely Callaway's argument was that most golfers never play in USGA-governed competition, so a club that makes the game more fun should be allowed in casual rounds. Arnold Palmer, who had just signed a long-term endorsement deal with Callaway and was the USGA's national chairman of its members program at the time, agreed publicly. "This club is not a threat to the integrity of the game," he said. "The USGA should help people enjoy the game."
USGA executive director David Fay saw it differently and called the idea of allowing non-conforming clubs in recreational play "a recipe for anarchy."
Could tour players use the ERC II?
Not on the PGA Tour or in USGA events. But in 2001 the R&A still had no COR limit, so the driver was allowed at the Open Championship. Before the 2001 Open at Royal Lytham, Pierre Fulke, Mark McNulty and Phillip Price had all won European Tour events with an ERC II.
How did the fight end?
In May 2002 the USGA and R&A proposed a compromise: allow high-COR drivers for recreational golf for five years starting in 2003, but not on pro tours or in national Opens. In August 2002 the USGA reversed course and kept the 0.830 limit for all U.S. golfers, including anyone posting a handicap score. The R&A adopted 0.830 for the Open and recommended it for pro tours from January 1, 2003, and left amateurs in its regions without a COR limit until 2008.
Callaway said it was "disappointed but not surprised," offered to exchange ERC II drivers bought during a recent promotion for a current model, and kept selling high-COR drivers outside the U.S. Since 2008, one limit has applied to golfers everywhere.
What did the ERC II change?
- It made "conforming" a word everyday golfers knew.
- It forced the USGA and R&A to line up on one driver standard.
- It showed equipment companies would argue with the rule makers in public, a fight that came back with square grooves. Read the history of the golf wedge for the 2010 groove rule.
Every modern driver, from the Callaway Epic to the latest models, is engineered to sit right at that same limit. Read where Callaway's A.I. face work began or the full history of the golf driver.
Is an ERC II worth buying today?
Only as a collector's piece or for casual rounds. It is still non-conforming, so you can't use it in a handicap round or a tournament under USGA rules, and a modern 460cc driver will be more forgiving. If you want a Callaway driver you can play anywhere, browse used Callaway drivers or see our best used drivers under $200. Have an old driver in the garage? See what your clubs are worth.
Frequently asked questions
Is the Callaway ERC II legal?
No. It does not conform to the USGA and R&A limit on spring-like effect, so it can't be used in competition or for posting handicap scores.
How much did the ERC II cost new?
Callaway's suggested retail price was $625 in the United States.
What is the COR limit for drivers?
0.830, now measured with a related pendulum test called characteristic time.
When did the R&A adopt the limit for everyone?
2008. Before then, amateurs in R&A regions had no COR limit.
Sources: Callaway Golf press releases (Oct. 24, 2000 and Aug. 6, 2002), Sports Illustrated (Oct. 30, 2000), Christian Science Monitor (July 20, 2001). Last updated October 2026.
