Pictured below is my Mitt tennis racquet. I turned it on its side because that's where it's different . The racquet has these little silver plastic things ....I'm not sure you can see them. Anyway the strings go over them it they cause the strings to move or "rock".....similar to the old Wilson rollers.
Mitt claims to be the only racquet with moving parts.....but then the rollers tried the same thing in a different way .
It allows for a real comfy feeling and I think puts a bit more spin on te ball.