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Notice to Manufacturers: Clubhead Moment of Inertia Test and Limit February 14, 2015

On Aug. 30, 2005, the USGA published a proposal to implement a test and limit for clubhead moment of inertia (MOI). The USGA Equipment Standards Committee received detailed written comments from manufacturers regarding both the proposed limit and the accompanying test procedure. After careful consideration of the comments received from equipment manufacturers, the USGA has approved the implementation of a clubhead moment of inertia test and a limit of 5900 gm·cm2. Additionally, a test tolerance of 100 gm·cm2 will be used. The limit applies to wood-type clubs only. Other current clubhead requirements that may have an effect on MOI remain in effect. This includes such requirements as those relating to volume, head dimensions, and plain in shape. 

The procedure for measuring clubhead moment of inertia has also been revised to improve repeatability and accuracy. The changes from the original proposal were based on comments received from manufacturers and additional evaluations conducted by the USGA after the original measurement method was published. 

The test and limit become effective May 1, 2006. 

No clubheads that have been submitted to the USGA for a conformance ruling exceed the limit. 

Some of the written comments received from manufacturers provided the USGA with information that confirmed USGA findings that there is very little protection difference between the original limit proposed and the final limit chosen. The USGA believes that the limit chosen provides an appropriate level of protection against future unknown developments - including advanced materials that may become available in the future. This is consistent with past equipment rulings by the USGA that allowed some, but not unlimited, advances in technology.