The used plastics are polypropylene, technopolymer, and other polymer alloys. Polymer plastic is the most affordable and common option, compared to fiberglass and carbon fiber, but don’t let that fool you into thinking it’s no good. In fact, it can make for some sturdy, durable, and resistant fins and survive bumps and scratches, making it ideal for beginners.
The catch is these fins’ “memory” characteristic. With extended usage and because they’ve bent too many times, you’ll notice them losing their shape and stiffness and molding into a curved design.
This is problematic because it means less snap, and consequently less power transfer, so a kick with a curved blade won’t give you as much energy as one with a straight blade. These fins could also be too stiff for smaller freedivers.