A 2.5" centre trailer — 4.88 square inches of fin — for the fifth box on a quad or the rear box of a thruster. 2.50" deep on a 2.62" base, in solid fiberglass. It is a centre fin small enough to change how a board feels without adding a fin's worth of drag: run it as the fifth fin behind a quad, or drop it into a thruster's rear box in pla