Specifications ◆ Model Name: C・A・R・D - 3/3 ◆ Material: Carbon ◆ Weight: 3g This is the SD90 spacer "C・A・R・D - 3/3," which is initially included with high-grade models like the SD510 and SDS510. What CARD stands for: C - Carbon fiber / Lightweight and strong carbon fiber A - Align center / Guide function to direct the tuner to the correct position R - Resonant / Improves vibration transmission by eliminating the space between the tuner and the head D - Defend / Prevents installation marks and paint cracks on the head caused by the tuner itself The most important part is the 'R'! ★ To put it simply, the effect is: It improves the sound by increasing the contact between the tuner and the guitar head, allowing the string vibrations to be transmitted firmly to the neck. It's great that there's an item like this that has no drawbacks and is easy to understand! When Kluson-type tuners are installed on a guitar head, a large cavity is created at the base of the post. When you think about it, the part of the Kluson tuner that contacts the head is much smaller than that of a Grover-type tuner, and this shouldn't allow string vibrations to be transmitted properly to the head. This is a structural defect of Kluson tuners, and there is no good way to improve it. Even those using vintage tuners have given up on this part, calling it "play." This C.A.R.D is an innovative product created as an answer to such a long-standing problem. With this lightness and this robustness! And with just the right amount of softness, it achieves a high degree of adhesion, making it a product that can truly be called a crystallization of modern science. A patent has already been applied for by GOTOH, so it can only be manufactured by GOTOH! Please refer to the GOTOH official website for details such as the length and diameter. ※ The machine heads (tuners) themselves are not included in this product for sale. The item in the first photo is the product. Accessories/Parts...Pegs