Double Lock Design - Clamps directly onto the archwire in both the upper and lower without having to take the archwire out. Double Lock Design - With Titanium Clamps and Screws. Continual Dual Force Technology for fast, yet gentle continuous forces to the maxilla and mandible.Class II and Class III Correction.No Assembly or Lab Work Required.Treats both Extraction and Non-Extraction Cases.Ideal for Non-Compliant Patients Two Sizes available.Class II Measurement:Have the patient bite down.Measure from the distal edge of the Lower Cuspid Bracket to the Mesial End of the Upper 1st Molar Tube.Minimum to Maximum   27mm - 36mm    Standard  #424-215TiMinimum to Maximum   23mm - 32mm    Small   #424-216TiClass III Measurement:Have the patient bite down.Measure from the distal edge of the Upper Cuspid Bracket to the Mesial End of the Lower 1st Molar Tube.