The pendulum device will require only a low speed strike to the clubface by a small weight on a pendulum. The device will measure the contact time of the collision between the two objects. The longer the contact time, the greater the spring-like effect of the clubface. The time measured is called the Characteristic Time of the clubhead. The new test will not change the status of clubs previously ruled conforming or non-conforming.
The Characteristic Time limit set for conformance is 239 microseconds, plus a test tolerance of 18 microseconds. The protocol for the pendulum test is available on the USGA website.
The proposal, issued in February 2003, also has been adopted by The Royal and Ancient Golf Club of St. Andrews, which is the governing body for golf outside of the United States and Mexico. The USGA is the governing body for golf in the United States and Mexico.