In Stock. 45 Day Lowest Price - 100% Satisfaction Guarantee. This may be the best shoulder rest design ever! Ergonomically designed to be one of the most comfortable rests on the market today, the Mach One is completely hand carved. The feet are molded out of 100% nylon so there is no risk of scratching your instrument. Try one today, you will be amazed at the difference. Adjustable for small and large viola.