The CrazyFly fins are "Razor" sharp. We have designed them with very thin profile to cut easily through water, prevent drag and make the boards faster. Razor fins also provide flex to some extent, which allows for comfortable carving and transitions. Lots of R&D has been put into invention of this incredible material. Razor fins are made from DuPont high quality polymer filled with fiber glass fibers. This material is also used in aerospace technologies and provides extreme durability, light weight and superior strength.