GUILLAUME Rosin in Aluminum Can I just bought this year, but I've used it a few times, so there's a sense of use. The amount hasn't decreased much, but there are thin cracks on the surface. I was using it for violin. The following is a product description by the manufacturer: This is a high-quality rosin made from 100% natural French resin, skillfully blended according to the unique recipe of the Belgian bow master "Pierre Guillaume". It combines solid resin and liquid resin, and has excellent viscosity that brings out outstanding sound quality. This rosin was immediately accepted not only by violinists, but also by violists and cellists.