25 Soft is recommended for divers under 175lbs or surface swimming where a dynamic performance is the aim over sudden movements and overcoming negative buoyancy during rapid movements like spearfishing action.
30 Medium is ideal for Freedivers weighing between 175-200lbs that require a balanced stiffness to compliment their body weight and a mix of shallow, mid-depth, deeper diving to 30 meters (100’).
40 Stiffer blades are still softer than the typical Mfg’s stiffest blade and are typically well suited to divers weighing over 200lbs. The ideal application of a stiff blade for divers under the 200lb+ weight level is typically for deep spearfishing past 30 meters. In this environment a fast accelerating fin that generates sudden thrust is preferred to overcome additional negative buoyancy, current, and sudden changes in depth and variable conditions encountered in challenging spearfishing conditions.