Matt 'Mayhem' Biolos's 'MB' shaper fin. High area specialty quad set adds bite and control. Upright keel template designed for traditional fish shapes. Overview Matt 'Mayhem' Biolos's specialty quad fin set. High area quad keel set adds bite and control to hybrid boards with wide tails, without sacrificing pivoting capabilities. Board Types Designed to fit the FCS II Fin System. Recommended for all board types including modern fish and hybrid models with moderate-to-low rocker.