This is our classic Standard Issue Series fin. Do not be fooled by the name, as this fin has some very good design features that remain timeless. The shape was developed in the late 1970‘s, and the SI fin has been delivered on Bananas, San-O‘s and Rapiers since their inception, with amazing success. Fin Rake is the distance that the rearmost tip of the fin hangs past the rearmost base of the fin at board level (this is not the fin tab). Many years ago, I realized that too much Rake in this style of fin will hinder the rotational effect, and turning is one big rotation. If the fin is too verticle, it actually slows the board, and it also will hang up on foreign objects such as kelp. The SI Series fins have just enough Rake to rotate properly, and enough Base for plenty of snap out of a turn.