What are these fins on the Beechcraft 1900? Here's an image for you to see these little fins. What are they used for?


Source (image has been modified to indicate location of fins).
Well, those fins were put there to increase yaw and pitch stability on the D version because of the change in the centre of gravity due to a higher fuselage from the C version. This D model also had more powerful engines than the C model. To add on, the strakes at the bottom were added for the same reason too.

More info can be found here.