Side Wave RTM CARBON Fin SBTwo supplementary fins positioned on the rail help to track and guide with their main purpose being to provide additional grip in extreme turns. When railing the board up hard, the tail starts to come out of the water, for example during top turns (which then become lip slides) and also in extreme bottom turns. In these extreme situations centre or twin fins may come out of the water but one of the Side Wave fins will still grip! These fins feature a