87 FAA Chart Users’ Guide - IFR Enroute Symbology Off Route Obstruction Clearance Altitude (OROCA) AIRSPACE INFORMATION (Continued) Low Charts Only OROCA is computed similarly to the Maximum Elevation  Figure (MEF) found on Visual charts except that it pro- vides an additional vertical buffer of 1,000 feet in desig - nated non-mountainous areas and a 2,000 foot vertical  buffer in designated mountainous areas within the United  States. Example: 12,500 feet Low and High  Charts SFRA Symbology Example: Low L-13 Chart Special Flight Rules Area (SFRA) Example: Low Chart (Washington Area Chart)  Example: High Chart (H-12)