This is a Shinobigoma (silent bridge) for a slender-necked shamisen with two-stage volume adjustment (for a Jiuta shamisen's medium neck). Because the volume is low, you can practice without worrying about your surroundings. It's designed to prevent the bridge from shifting up, down, left, or right while playing. The string groove width is 11mm. The string groove can be modified. An instruction manual and one spare sticker are included. Thank you.