The "S" shape, ergonomically designed molded plastic provides maximum comfort and durability. This model has a leather strap allowing slight suspension and movement on the shoulder and the strap use is optional. This rest fits comfortably on your shoulder and is considered one of the most comfortable rests on the market. The sculptured shape of the all Mach One Shoulder Rests mold perfectly to your shoulder. The "S" shape fits comfortably on your shoulder and minimizes the size of the feet. These are molded from a single piece rubber and have a lifetime guarantee. They will never touch the ribs of your violin and will not scratch your valuable instrument.