I put it on my racquet but haven't played it yet 'cause my tennis season is over. Of course I still swing my racquet indoors.
I know there is a long post on it in the archives so search for it.
It does work.
Basically it works like this:
Most knives handles are oval shaped in their cross section. The Wonder Wedge changes the handle into a D shaped like Shun knives.
Some people will like this shape and some people dislike it.
Just swinging the racquet I like it. I feel like I get a better grip and I get more leverage.
You can make the same thing by using balsa wood or very firm foam. I bought the Wonder Wedge because its a mass produced product.
Its not only for beginners. Actually if was called the luxilon super pro accessory I betcha you would buy it. It's for anybody that plays tennis and who wants to change the shape of their grip.
If you had to choosee between a poly string and a wonder wedge, I would get the wedge.