The Mach One Maple Hook Viola Shoulder Rest is crafted in Canada of North American Maple; The Hook is a mere 5mm thick. It’s known for being even more ergonomic than the famous original Mach One, designed with the new “Hook” model that rises to new levels for the comfort of the busy player. Luthier Peter Mach's intent in designing the hook was for the shoulder rest to hug the shoulder even more, for a more comfortable fit. The viola model will easily fit violas with lower bouts in the 230-266 mm range, between 9" and 10 1/2".