it's a foam that you use to make a bottom bait lift off the bottom!! And i have been useing it for a while now and i have never had a carp take it off my hair. i use a pellet stop the v ones that sets in the pellet so it makes the foam very hard to come off even bye me pulling at it. If i didnt think it was safe i wouldnt use it. I have seen other people use it and non have ever really said its come off. I am sure it cant do that much harm to the fish or no company would make it to use with baits hope thats cleared up every thing