Superflite Pre Shrunk finish tape is the same as regular finish tape except that it has been pre shrunk at the factory.  This is especially useful on straight tape runs such as over ribs or fuselage stringers on the top of the airplane where it may be exposed to excessive heat from the sun.  This is particularly important if you are using a dark color topcoat and/or live in a hot environment.  Using a normal tape in those conditions will sometimes cause the finish tape to shrink a little and pull in exposing a narrow strip of fabric to UV light.  Eventually the fabric will tear along the tape edge.  This can be seen when inspecting a wing through an inspection panel in a sunlight.  *Remember, if you are using a preshrunk tape on a perimeter, you will not be able to heat form it around a curve.