Mega 3d is a refinement of Zone 3d. We offer FFF, FH1, H12, 123, 246, 357, and 468 densities., see below for more information: FFF: Float + Float + Float FH1: Float + Hover + Intermediate H12: Hover + Intermediate + Sink 2 123: Intermediate + Sink2 + Sink 3 246: Sink 2 + Sink 4 + Sink 6 468: Sink 4 + Sink 6 + Sink 8 SalaFinder 3d line specification and recommendation: Size weight Length US rating Euro Rating 490 490gn 37' 5/6 530 530gn 38.3' 5/6 6/7 570 570gn 39.7' 6/7 7/8 610 610gn 41' 7/8 8/9 670 670gn 43' 8/9 9/10 730 730gn 45' 9/10 10/11 790 790gn 47' 10/11 11/12