uxcell Acoustic Electric Guitar Feedback Buster Hollow Knotting Pattern Wood Sound Hole Cover Block Protector Product Name: Guitar Hole Sound Cover Material: Wood, Sponge; Total Size: 105 x 9mm/4" x 0.35"(D*T) Fit Hole Dia: 98-101mm/3.7"-4" You can restore the sound hole piano body resonance sound field Wood can play a silent role in the mat, completely fit the soft side