Grip Size
The thickness of the grip - undersize, standard, midsize, or jumbo - which affects hand action, comfort, and shot shape.
Grip size is the diameter of the grip on your club, and it comes in standard categories: undersize (junior/small), standard, midsize, and oversize (jumbo). It is fitted primarily to hand size and finger length, but it does more than provide comfort - grip size influences how freely your hands can rotate the club through impact.
A grip that is too small encourages overactive hands and can lead to hooks; a grip that is too large quiets the hands and can leak shots out to the right. The traditional fitting starting point is glove size and a measurement of hand length and finger length, then refined by feel and ball flight.
Grip size is adjusted in two ways: choosing a different grip model, and adding layers of build-up tape under the grip to bump the diameter up in increments. Players with arthritis or hand pain often size up for comfort, accepting the effect on hand action as a worthwhile trade.
Because grip changes also affect swing weight - a heavier or larger grip shifts the balance toward the handle - grip fitting touches feel as well as fit. It is one of the cheapest specs to change and one of the easiest to ignore.