You're really not going to be able to achieve any sort of astounding increase in your wrist size -- there's just not that much muscle there (it's mostly in your forearms) to increase in size. QUOTE]
The circumference of the wrist is determined primarily by the size of the bone and the thickness of the subcutaneous fat. If you roll-up your sleeve and open and close your hand you will notice that the muscles actual producing the movement run the entire length of your forearm. Similarly, if you hold your forearm parallel to the floor and move your hand up and down from the wrist, you will notice that the muscles in your forearm again are responsible for producing the movment. The exercises mentioned will develop those muscles, the bulk of which will be in the middle and relatively little of which are in the joint itself. I think dsvirsky is right-on. I don't think there is much you can do to increase the size of the wrist itself.