Every Mermaid Tail Comes with a monofin. A monofin is a very important part of the mermaid tail. Not only does it provide a beautiful shape, but it also helps you to swim faster and build leg strengh. We reccomend swimming with the monofin alone to learn the dolphin kick technique before swimming in your new tail. We offer 3 differnt size Monofins: Child, Youth, and Adult. All fins come with and adjustable foot strap and are custom cut. If your not sure which monofin is right for you please contact me @ 305-316-9881.