This new Thomastik-Infeld violin rosin supports focus, attack, and brilliance, helps improve the strings' resonance and makes clear articulation easier. So by using this rosin, you can get even more tonal variety from our Thomastik-Infeld strings. The rosin comes in two parts: the main rosin and an additional booster. This booster is a separate rosin which adds additional warmth in the sound and stronger hold when playing. The rosin comes in a metallic container with a magnetic opening and closing mechanism which will make the rosin easy to use.