Designed especially for our amplified players, these magnets help to reduce extra resonance in your Forte3D cello. After placing the silver magnet inside the cello you can simply move the black leather wrapped magnet around on the back of your instrument until any pesky frequencies are obliterated! See pics for instructions. They can also be used to replace your larger C string Jaunty (low B natural) wolfstopper! (FYI, if you have a V1 cello these magnets can get stuck on your internal spring wolf stopper so be a bit careful when you're installing them.)