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

- revised design improved fitment -

- successfully used in Hawaiian 4-8' swells -

FCS II Adapter or US Box base see listing  www.ebay.com/itm/204626716582

• Futures adapter fits center and rear quad fins with a 1/2" Futures fin base. Includes futures screw.
  
  
• Printed in PETG on a Bambu Labs 3D printer
  
  
• Longboard fin screw and plate not included
  
  
• This adapter fits Longboard (Fins Unlimited) fin boxes (ex. fits True Ames, Rainbow Fins, FCS/Futures Longboard Fins)

Choose the correct longboard 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)
  
  
• This is the correct adapter if your fin box says Futures Fins ILT made in Huntington Beach, Fins Unlimited Encinitas or FCS on the inside bottom
  
  
• If your board uses a US Box base which is common on non USA boards see this listing  www.ebay.com/itm/204626716582

Sold by DISTEL3D LLC. Use at your own risk.