From 1 January 2010, the Rules on club face markings include the following three additional specifications for clubs other than driving clubs and putters:
The total cross-sectional area of a groove divided by the groove pitch (width plus separation) will be limited to 0.0030 square inches per inch (0.0762 mm2/mm);
Groove edge sharpness will be required to be substantially in the form of a round having an effective minimum radius of 0.010 inches (0.254 mm). This limit will only apply to clubs with lofts of 25 degrees and above.
Grooves will be required to be plain.
As previously intimated (see Section 5c), these new specifications only affect new models of clubs manufactured on or after 1 January 2010 and competitions where the Groove and Punch Mark Condition is in use.