JDM Golf Clubs and the Rule Book: What Non-conforming Means

“JDM”, for Japan domestic market, is shorthand among golfers for clubs made for Japan and sold there. Some are the same as the global range with a different badge; some have different heads, lofts, lengths and shafts; and a few are designed to a different rule. This chapter of The Atlas of Japanese Golf explains what the rule is, who sets it, what “non-conforming” means in practice, and what a buyer should ask.

What the rules limit

The Rules of Golf are administered jointly by the R&A and the USGA, and Appendix II sets out the specifications that clubs must meet. For drivers, the limit that matters here is the spring effect of the face, the “trampoline” by which a thin face returns energy to the ball.

• The measure. The limit is expressed as a characteristic time, the time for which a small pendulum and the face stay in contact. A longer contact time means a springier face.
• The number. In a letter of 6 November 2007, circulated in Japan, the R&A set out that from 1 January 2008 all drivers must have a characteristic time that does not exceed 239 microseconds, with a tolerance of 18 microseconds.
• The extension. In May 2015 the R&A circulated a proposal to apply characteristic-time limits to other clubs by category, and invited comments to be submitted by 15 August 2015. It was a proposal, and this chapter does not report how it was settled.

What “non-conforming” means

A non-conforming club is one that does not meet those specifications. It is not unsafe and it is not illegal to own, but it may not be used in a round played under the Rules of Golf, which includes competition rounds and, ordinarily, rounds played for a handicap. In a friendly round for enjoyment, it is the player’s choice.

Japan’s position

On 3 February 2015, ahead of the Japan Golf Fair in Tokyo from 13 to 15 February, the Japan Golf Goods Association, the trade body for Japanese golf manufacturers, said that it would support the distribution of non-conforming equipment, leaving the decision to each member company. GolfWRX reported that the association advocates clearly marking such products, without having specified how, and that its stated motivation was to cater to golfers seeking more enjoyment without the performance limits the rules impose. The report described Japan as the world’s second-largest market for golf equipment and observed that no major American golf manufacturer had a line of non-conforming equipment.

• PRGR Egg. The clearest example. A 2017 profile describes the Egg range as designs that break USGA and R&A rules, and notes that Japanese consumers will pay a premium for them. See XXIO, PRGR and Yonex.
• Other makers. Each member company makes its own decision, so the existence of a non-conforming driver from a given brand should be checked model by model.

The rest of JDM

Most JDM clubs are fully conforming, and differ from export models in other ways.

• Different heads and shafts. Mizuno Pro is sold in Japan only and made fully to order, and the MP Type-1 and Type-2 drivers were Japan-only models. See Mizuno and the Chuo Forge.
• Different labels. Miura-Giken is the label for Miura clubs sold only in the Japanese market, with slight modifications for it. See Miura Golf.
• Earlier arrival. A 2009 comparison for UK readers noted that the Japanese market had received a major maker’s driver for several months before Europe, and that a Japanese version of one set of irons had less offset and lofts one degree stronger. Both are dated observations, but they illustrate how a domestic version can differ in numbers that matter.

Questions to ask before buying

• Does the club carry a conformance statement, or a non-conforming label? If it does not, ask for the model name and check it with the maker.
• Is it a domestic version? Ask for the loft, lie and length as built, not as catalogued.
• Will you play it in rules-governed rounds? If so, a conforming club is the only safe choice.
• Is it a collector’s piece? A non-conforming driver may be exactly that, and its condition and completeness matter more than its performance.

Our descriptions record the model name and the specification as built. The buying guide explains flex and head-speed pairings.

Read next: Japanese Golf Brands Compared: Forging, Faces and Feel and Why the World Buys Japanese Golf Clubs.

Continue reading

• The Atlas of Japanese Golf: Makers, Methods and Why the World Collects Them
• Why Japan Became Golf's Great Workshop
• Mizuno and the Chuo Forge: Feel as Engineering
• Miura Golf: A Himeji Family Forge
• Epon and Endo: The Forging House Behind Other Names
• Honma Golf: Stars, Gold and the Sakata Workshop
• XXIO, PRGR and Yonex: Clubs Built for Ease and Speed
• Directory of Japanese Golf Brands
• Buying Golf Equipment from Japan
• All collector guides

After a particular Japan-only model? Our Hunting Salon™ searches across Japan's private collector circles on your behalf.

Index terms: jdm golf clubs · non conforming golf clubs · japan domestic market golf · japan golf goods association · prgr egg · r&a characteristic time 239 microseconds · golf rules equipment appendix ii · mizuno pro japan only · miura giken

References

Dates and figures in this chapter were checked against these pages. Where accounts differ, the text says so.

• The R&A, letter on the spring-effect limit for drivers (6 November 2007), hosted by the Japan Golf Association
• The R&A, notice to manufacturers on spring-effect interpretation (8 May 2015), hosted by the Japan Golf Association
• GolfWRX, Japan Golf Goods Association endorses sale of non-conforming clubs (3 February 2015)
• MyGolfSpy, Know Your Japanese Brands: PRGR (2017)
• Golf Monthly, Japanese golf brands (26 November 2009)