This is what I used, happy with the application process, and the results from the year it has been on the plane.
I bought the 6" width, and split it into two 3" pieces.
A friend of mine here uses the soft fuzzy side of some adhesive backed industrial Velcro on the under side of the top wing skin, rather than stick UHMW tape to the painted flap surface. It seems to work well, I plan to do the same some day.