FCS 2 Al Merrick PC Aircore Thruster Surfboard FinsFins with AirCore Technology feature a pressed polyurethane foam core that mimics the geometric foil of the fin. AirCore technology reduces the amount of fiberglass required in the RTM moulding process making it much lighter while allowing total manipulation of the flex. Performance Core fins have a progressive flex throughout helping the everyday surfer maintain drive and speed through turns. Performance Core fins are versatile, very responsive and