Eduardo's essay on this edge board.
This sort of rail desing has two different improved features: less drag at high speed and a little extra hold. Essentially you got deeper concaves, as the bottom is narrower if you let the rails apart, on a wider board. Better rail to rail transitions and better water flow under the hull.
And, obviously you got a brand new hardish edge in addition all the way up to the nose, so, a bit of an extra grip on turns.
The rest of the shape is a well balanced short midlenth single fin. Flat and smooth.
Comes with a directional sanded mint bottom and rails plus a polished resin panel on top.
width 20 3/4
Nose width 16
Ttail width 14 1/4