New design - lies very close to the palate - less crown tipping. Orthogonal location of arms (perpendicular to screw travel) resists "turn-back" and applies force to center of resistance. Body is 30% smaller than typical Expansor RPE - ideal for narrow maxillary expansion. Directional arrows on BOTH body sides - allows inverted placement. Will not expand past design max. - no over treatments. Includes one type B swivel key.