Finis Trainer 1 Monofin LImprove your kick with the Finis Trainer 1 Monofin L. It will help you develop a powerful, hip generated dolphin kick. This monofin was made for advanced swimmers and triathletes. It is great for strength training, it can help build abs, lower back and quads. It is made with a long fiberglass blade. A great addition to your workouts.[Details] Aids in lengthening stroke and improves body balance Increases range of motion in feet and ankles Model: 1.