TMS Kobo Original Sound Improvement Goods: Spacer-kun This is a product that goes between the body and the screws used. It's intended for use when you want a little more resonance or resistance. It's not just a solid block; it has a cavity inside to produce resonance. We've gone through many prototypes to determine the size and volume of the cavity. It should work with any manufacturer (Yamaha, Yanagisawa, Selmer). Price is per piece (regular price: 2500 yen). TMS Sound Improvement Goods