The SUAD is also a custom-made appliance that is made of a heat-sensitive acrylic and is reinforced by a metal framework. The SUAD adjustment mechanism (Herbst) is positioned on the sides of the device and consists of a piston that slides within a tube. The appliance is comfortable on the teeth and the mechanism allows good freedom of movement of the jaw. Therefore it is used frequently in patients who tend to grind their teeth heavily. The position of the jaw can be adjusted by using small rings that slide over the piston and when the tube is positioned over the piston it will advance the jaw the width of the ring. Small elastics (rubber bands) are used to keep the jaw from falling open during the night although the patient is able to partially open the mouth, which can improve comfort when using the appliance.