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 Attachment" is a part that is passed through the string to make the ball end spherical. By making it a spherical end, ・Prevents damage to the back plate of the bridge due to spherical contact! ・The sphere firmly presses against the pin groove, stabilizing tuning! ・Because it is spherical, the contact surface is uniform, and string vibrations are transmitted firmly, improving balance! ・Eliminates the unevenness of the ring-shaped end! ・Fully demonstrates the potential of the guitar! ・Helps in pursuing your favorite sound quality by the difference 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 Total 6 pieces in a set 【Differences by Type】 The stable effect will be demonstrated in 2-3 days after installation. Please refer to it for selecting the best match for each 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 processing. 【User Impressions】 Absolutely no complaints! I have repeated the purchase many times. I tried installing about 10. There was not a single acoustic guitar whose sound became worse, and the volume increased and the tone came out firmly. Solid-top guitars have a deeper resonance, and plywood folk guitars can be enjoyed more roughly and powerfully. I enjoy combining all types by purchasing them. I have been playing acoustic guitar for about 30 years, and I don't think there is a practical item as simple and logical as this. When I put it on an acoustic guitar in the 50,000 yen class, it sounded like a 100,000 yen class guitar! Thank you for experiencing the effect. 【About Shipping】 We will ship by regular mail (3-4 days for arrival). An item you'll want to have along with a capo/guitar shield/tuner/effector/guitar stand/pick/ guitar amplifier/strap, etc.! Patent Office Design Registration No. 1483662