The all-round fin is the perfect blend of rake and surface area - providing stability that will give you confidence. It can be ridden as a single, in which case you would match the size (in inches) of the fin around the size (in feet) of your longboard. If you want to ride it as a 2+1 setup, ride it somewhere between 6 and 8 inches, depending on your board length.
The all around fin will feel great with longer sweeping turns and still provide plenty of hold in the tail while you cruise down the line. It works in boards of all shapes and sizes and almost any surf conditions. Tried and true!