Guitar strings material:High quality brass, good toughness, hard to break,Anti-oxidation coating significantly protects strings against common corrosion and extends life span Package includes:1 Sets acoustic guitar strings(6pcs in brass3pcs guitar picks and 1 string changing tool) Hold Tune Stable Sound:Our acoustic guitar strings offer a long lasting, warm, bright and balanced acoustic tone with an expressive, vibrant presence. Sound can be transmitted to resonance boxes very well Guitar string diameters: 6 Diameters includes 1.33 mm/0.052 inch,1.06 mm/0.042 inch,0.81 mm/0.032 inch,0.6 mm/0.022 inch,0.38 mm/0.015 inch,0.28 mm/0.011 inch Quality Service:Please contact us with any questions about acoustic guitar strings and We offer you a 30-day no-questions-asked return servicewe will give you a satisfactory answer within 24 hours.