Considering your build, strength and fitness level is very important when choosing which will best suit you and your type of freediving. Always use your ideal, lean bodyweight when using this guide. This will correctly match your muscle mass and strength to the correct blade type and stiffness. If the chart recommends two options where the bars cross over - the diver should choose based on whether they like a softer or stiffer feel to the fin. We recommend the softer option for the greatest efficiency. The stiffness comparison scale indicates how each model compares within the 72cm blade range. Divers under 165cm should consider the P620 range of fins. The shorter blade length will have less leverage over the knee joint promoting better fining technique and will be less likely to induce fatigue or joint soreness. Penetrator fins offer 3 main types of stiffness:  
10 (X-SOFT), 20 (SOFT),
30 (MEDIUM)