The Core-X Jig Heads were designed for use with umbrella rigs or swimbaiting in open water. They have a strong black nickel Mustad hook and barb to help keep your soft plastic swimbaits attached to the hook. More specifically, these heads can be inserted inside the cavity of the Hollow Core-X Swimbaits in order to hide the lead head and get the most out of each swimbait by preventing them from tearing up as easily. The heads come in various sizes to accommodate each brand and type of swimbait or grub around and come 4 per pack.