Convert a single fin box to fit any FCS fin. Features Shipping Overview Change from a traditional longboard fin to a FCS thruster set up in seconds. Allows your longboard to take a smaller FCS 1 centre fin. We offer: Express Shipping: Select Express 2nd Day Shipping at the Checkout for an additional fee of $15. Tracking: Quick & easy online tracking. Peace of Mind: All our deliveries are fully insured against damage. Returns: 30 day exchange or refund for unopened items.