Thank you for visiting. We would appreciate it if you could also take a look at the comment section. When purchasing, please specify the "material and size". "Guitar String Attachments" are parts that are passed through the strings to create a ball end. By using a ball end: ・Prevents damage to the back plate of the bridge due to ball contact! ・The ball firmly presses into the pin groove, stabilizing tuning! ・The spherical shape provides uniform contact, allowing string vibrations to be transmitted properly, improving balance! ・Eliminates the uneven orientation of ring-type ends! ・Fully utilizes the potential of the guitar! ・Helps in pursuing your preferred sound quality through differences in types! 【Types】 Brass: Outer diameter 4.0mm size set Brass: Outer diameter 4.5mm size set Aluminum: Outer diameter 4.0mm size set Aluminum: Outer diameter 4.5mm size set 【Product Contents】 4 pieces for strings 1-4 2 pieces for strings 5-6, for a total of 6 pieces per set 【Differences by Type】 The effects stabilize within 2-3 days after installation. Please use this information as a reference for selecting the best match for your individual guitar. Brass material : Bright and lustrous tone Aluminum material : Gentle and calm tone Sustain : 4.5mm size < 4.0mm size Sound thickness : 4.0mm size < 4.5mm size 【Compatible Strings】 Acoustic guitar strings: Extra light to medium gauge compatible * Can be installed without modification. 【User Impressions】 Absolutely no complaints! I've repeated purchases many times. I tried installing them on about 10 guitars. Not a single acoustic guitar sounded worse, and the volume increased with a clear tone. Solid-top guitars have a deeper resonance, and plywood folk guitars sound more powerful and crisp. I purchased all types and enjoy mixing and matching. I've been playing acoustic guitar for about 30 years, and I don't think there's a practical item as simple and logical as this. When I put them on a 50,000 yen class acoustic guitar, it sounded like a 100,000 yen class guitar! Thank you for experiencing the effects. 【Shipping】 Shipped via regular mail (takes 3-4 days to arrive). An item you'll want to have along with a capo/guitar cable/tuner/effector/guitar stand/picks/guitar amp/strap! Patent Office Design Registration No. 1483662