section_path: Design/Legs/fins
section_name: fins
paragraph_text: fins
  
  Boosters that will be deliberately expended do not have legs or fins. Recoverable boosters include four extensible landing legs attached around the base.
  
  To control the core's descent through the atmosphere, SpaceX uses grid fins that deploy from the vehicle moments after stage separation. Initially, the V1.2 Full Thrust version of the Falcon 9 were equipped with grid fins made from aluminum, which were eventually replaced by larger, more aerodynamically efficient, and durable titanium fins. The upgraded titanium grid fins, cast and cut from a single piece of titanium, offer significantly better maneuverability and survivability from the extreme heat of re-entry than aluminum grid fins and can be reused indefinitely with minimal refurbishment.