This appliance is used for pre-maxillary and lateral development when patient compliance may be a concern.  The midline expansion screw is placed in acrylic that it finished up against the anteriors.  The two laterally placed expansion screws provide the desired pre-maxillary development, while the midline screw can provide any needed lateral development, up to 3mm to 4mm. 

The appliance as shown utilizes bands only on the molars.  If desired, the occlusal rests on the first bicuspids can be replaced with bands, allow bonding the rests to the occlusal of the bicuspids often is sufficient.