The2Tails Mermaid Tails For Swimming With Monofin by Exclusive Style Swimmable Mermaid Tails Purchase Includes: The2Tails Monofin ($59.95 MSRP) and FREE Backpack ($16 MSRP). Tail arrives assembled and ready to use (top is sold separately) We use a 4-Way stretch, 360gram nylon/spandex mix fabric (competitors use 280 grams) Tails are made in the USA. Our UNBREAKABLE MONOFIN has a LIFETIME GUARANTEE USA orders ship the following business day and arrive within 2-4 business days.