Stiffness of Shaft
Partial transfer of energy from wrist action. Flexible shaft stores energy at swing motion giving more repulsion of shuttlecock at impact from the racket. Good for defensive and control play style (clears, overheads, returning smashes, etc...)
Stiff (Limited Flexibility)
Reasonable transfer of energy from wrist action, good for both defensive and offensive play style
Extra Stiff (Minimum Flexibility)
Maximum transfer of energy from wrist action. Minimum shaft movement gives high accuracy on shuttlecock positioning. Ideal for offensive play style (smashing, net kill, etc...)
Understanding Yonex Racket Codes
All genuine Yonex rackets have 2 sets of Laser-Etched serial number, one on the shaft, the other on the cone.
Shaft (7 digits) - Example: 1234567
This number is unique, like the finger-print, to each racket.
Cone (6 digits + 2 alphabets) - Example: 110562JP
The first 5 digits show the date of manufacture of the racket. In the case of the above example, the racket was manufactured on 11th May, 2006. The meaning of the last digit remains a mystery. The 2 alphabets denotes the Code of Distribution. The Code of Distribution is intended to show the country or the market in which the racket is officially to be sold, or the market group by which the racket is intended for use. In the above example, JP stands for Japan.
Below are some examples of Code of Distribution:
AS = Australia, BX = Belgium / Netherlands, CD = Canada, CH = China, CN / CP = Chinese National Team, DK = Denmark, FR = France, GR = Germany, HK = Hong Kong, ID = India, IN / IP = Indonesia, JP = Japan, KR = Korea, MA = Malaysia, NZ = New Zealand, SD = Sweden, SP = Singapore, TH = Thailand, TW = Taiwan, UK = United Kingdom, US = USA
To-date, there is no published literature and data from Yonex indicating the differences between rackets of different country codes.