These are standard type erhu strings made by Suzhou National Musical Instrument Factory, a long-established musical instrument manufacturer in Suzhou, China, under the "Huqiu" brand. They use soft steel, producing a bright and clear tone. They are an excellent match for Suzhou erhus. For "erhu strings," please tune them to A (outer string) and D (inner string) using a tuner. When storing, keep them in a dry place and be careful not to twist or apply pressure to them.