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Grip sizes | Golf Monthly
It's to do with the butt diameter of your shafts.
If you put a .60 grip on a .60 shaft it will fit correctly with the 1 layer of tape.
If you put a .58 grip on a .60 shaft it has the effect of adding the equivilent an extra layer of tape.
To give you an example, I use a standard size grip but need 3 build up layers + a layer of grip tape (4 layers total).
When I re-gripped mine I put a .58 grip on my .60 shaft (True Temper DG) so only needed 2 build up layers + the grip tape (3 layers) as the .58 grip on that size shaft is a little thicker and adds the extra layer.
Hope that helps :thup: