WD Music Products - Bass Guitar String Ferrule - String Bushing - Black - Qty 4 I.D. = 19/64 in. or .3 in. (7.63mm) Insert Dimensions = 3/8 in. or .37 in. (9.4mm) Collar Dimensions = 31/64 in. or .49 in. (12.46mm) Quantity 4 Bushings included Color: Black