Violin practice mute. Used to significantly reduce volume of the instrument for practice purposes. Not intended for performance. Reduces sound by up to 80%. Care must be taken with metal mutes, the bridge must be pulled up as the mute is pushed down to avoid excessive pressure from the bridge to the faceplate. Always check the mute is secure before playing. 

Due to their weight, metal mutes have the most significant volume reduction of practice mutes, while keeping a more detailed tone as compared to rubber mutes, which can produce a muffled tone unless reinforced with metal.