Yonex handles are about 1/16" larger than Wilson and Volkl handles, or about 1/2 size. As many have noticed, Yonex uses a thinner base grip on their racquets, thinner by about 1/16", so with the grip that comes from the factory, Yonex handles are roughly equal in size to other brands'.
Initial grip size: 4 3/8 with yonex original base grip. Yonex base grip thickness 1.6mm, weight 12 grams. Bare handle size: 4 1/8, bevel 1 width: 1.2mm, bevel 2 width: 1.1mm, bevel 3 width: 1.15mm. I change base grip to wilson cushion aire classic perforated, 2mm thickness, weight 16 gr after cutting to suit the bare handle.
More Yonex Tennis Racket Grip Size images
Amazon.com : YONEX EZONE 100 Tennis Racquet (Grip Size 4 3/8) : Sports & Outdoors
A tennis racquet’s grip size measures the circumference or distance around the handle, ...
Below would be in between 4 ¼ (Grip Size 2) and 4 3/8 (Grip Size 3) If you have a racquet handy (pun intended) but no measuring tool, here is another good way to get an estimated grip size. Pick up the racquet in a “hand shake” grip, if you can place your other index finger in the space between thumb and fingers then that grip size is probably a good place to start.
A typical overgrip will increase a grip by 1/16 inch. You can also increase grip size using a heat-shrink sleeve. One heat shrink sleeve will increase grip size by 1/8 inch. Both methods will increase overall racquet weight slightly (7-16 grams), but the benefits of a correct grip size far "outweigh" the disadvantages of this added mass.