Use your Futures or FCS II fins in a standard longboard fin box.
Ride your mid or longboard as a thruster or twin+1. 

 successfully used in Hawaiian swells 

 Now available to adapt FCS II and Futures fins

• FCS II adapter fits fin up to 5.25" long
  
  
• Futures adapter fits center and rear quad fins with a 1/2" Futures fin base. Includes futures screw
  
  
• Both versions available in white or black. Printed in PETG on a Bambu Labs 3D printer
  
  
• Longboard fin screw and plate not included

Choose the correct base to match your board

• This site contains a good explanation about the two different longboard fin boxes Which SUP Fin Base Option Do You Need for Your Paddle Board? (blackprojectsup.com)
  
  
• Longboard (Fins Unlimited): most common If your fin box says Futures Fins ILT made in Huntington Beach, FCS or Fins Unlimited Encinitas on the inside bottom then choose the Longboard (Fins Unlimited) version
  
  
• US Box: use if your board takes the larger longboard fins with the hump on the base. This fin base is more common on non-USA made boards.
  

Sold by DISTEL3D LLC. Use at your own risk.