The guy that designed them said he designed them because he hated fletching arrows. You can hear them going downrange but the sound you hear is from the back of the arrow. In other words when an arrow fletched with vanes or feathers is flying downrange you can hear it coming, with a FOB arrow you can't. I know what you're thinking(arrow has to be faster than the speed of sound) but I had my son stand off to the side of my bag target 20 yds away. The arrows with conventional fletching he could hear, and the FOB arrow he couldn't hear.
I've had fun shooting them but I don't know if I'm going to hunt with them. I still love feathers myself. One thing I don't like about them is they do alter your anchor point alittle. For $20.00 you get a bakers dozen so try them out, by the way the designer will e-mail you when you buy them ask you a few questions like which rest you're using, ect. He is very helpful, his name is Paul Morris. Also, I am in no way affiliated with Starrflight in case you're wondering....