On an aeronautical chart, airspace altitude limits for controlled airspace are typically depicted as:
Why →
On sectional charts, airspace altitude limits appear as a fraction. Ceiling over floor. In hundreds of feet MSL. "40/10" means 1,000 to 4,000 feet MSL. "SFC" as the floor means the airspace reaches the surface. This notation is used within the boundary lines on the chart for Class B, C, and D airspace.The trap →
Both ceiling and floor values are in feet MSL, not a mix of MSL and AGL. Many students assume floors are in AGL because Part 107 altitude limits are AGL-based, but sectional chart airspace notation is consistently MSL throughout. The only exception is SFC, which means the airspace starts at ground level.SOURCE → FAA Sectional Chart User's GuideCHECKED APR 21ACS II.A.K2MED