Maximum sound. The Vic Firth American Custom Keyboard Medium Hard Rubber mallets can be used on a range of percussion instruments. The mallet head consists of medium rubber for maximum attack while retaining some softness. With a birch shaft you can expect rigidity and a solid consistent feel. Perfect if you want the extra reach without the flexibility of rattan. With a 16 length these Vic Firth American Custom Keyboard mallets were designed for use on marimba xylophone and vibes.