This is a reed adjustment whetstone. The abrasive is fine for micro-adjustments. It's a tool to revive reeds that are difficult to use, such as those that are thick and hard to blow, uneven, or have absorbed water and swelled. Adjust by rubbing the flat part of the reed's underside against it, as shown in the second photo. Even though the underside of a reed may appear flat at first glance, it's said to be uneven at the nano level, and these irregularities negatively affect the sound. Just rubbing a reed against this whetstone can make a difference in the sound and playability. Size: 10cm long x 2.5cm wide x 1.3cm high Suitable for use with smaller reeds, such as Bb and Eb clarinets, and soprano and alto saxophones. This product is from a domestic specialist manufacturer and is finished with very high precision in terms of flatness. The offering is for the whetstone only. The reed in the photo is not included. #saxophone #clarinet #reed #wind_band