We have always tried to improve quality by selecting the best materials. SS-47 solder is no exception. We began by selecting tin as the base material.We know that sound quality is a function of the purity of the material. The purity of tin in ordinary solder is about 99.9% (3N) due to cost considerations.
SS-47 is made of high purity tin, with a purity of 99.993% (4N) or higher. Eliminating impurities to the utmost limit. It will charge additional cost (about 23-29USD).If it's better, we may use DHL or Japan Post's EMS.