These mallets are designed to the specifications of leading marching percussion specialist Jim Casella. This series has been designed to meet the demands of both the indoor and outdoor marching percussion ensemble. This extensive line of specially designed indoor/outdoor mallets, offers the marching percussion ensemble the one most extensive variety of timbres available today.Jim Casella Series Marimba Mallets feature highly polished birch handles, and a variety of rubber cores and latex combinations to create a full, rich tone and warm fundamental. They also offer an increased weight for added projection, and specially designed extra-durable synthetic yarn with a concert hall timbre. The IP13X is a heavier version of the IP13, built with extra weight in the core and an oversized birch handle to provide for a brighter articulation and extra projection.