Yamaha Silver 90

The Yamaha Silver 90, with sliding side bars so head weighting can be altered

Yamaha is one of the lost names of tennis racquet production, but their quality is second to none.
These are ceramic frames, which I normally do not go for since I find ceramics a bit toothless ususally. However, what makes these frames notable is the way you can alter the weight/head balance by moving plastic sliding panels on either side of the frame in order to generate more spin or more plough.  I am suprised this very innovative idea never caught on, but I imagine the patent was lost when Yamaha exited the tennis scene.  Maybe it is time to resurrect this idea...come on Wilson, give Yamaha a break and either buy the patent off them or allow Yamaha to re-enter the racquet market.

by moving the slide panel, head balance can be altered