The Reactor fins feature low rake (or sweep), which means their shape is generally upright.
The Reactor fins are built for quick reactions, easy maneuvering, and tight-radius turns. The upright design of these fins facilitates these types of turns, but in doing so sacrifices hold. This can be a good thing if you want to do fast, tight arcing turns and fit in the pocket on hollow waves, but it is less conducive to power surfing. Reactor fins tend to work best with boards that feature low rockers.