If your Studio 49 soprano or alto xylophone has a resonator box made entirely of wood, this is the set of replacement pins you need. This set of 30 pieces comes with 1/2 stiff metal nails covered with rubber, and 1/2 flexible rubber pins. This item is for one Studio 49 soprano or alto xylophone (contains stiff metal nails for between the bars, and flexible rubber pins for the bars to go on).