This is an adaptor for old style fin boxes allowing them to take FCS fins.
You’ll need:
1) an M3 thread for the back pin. Just cut the head off a stainless M3 bolt,
2) an M5 screw for the front of the tab and
3) a 2-3mm thick plate for the box tab with the M5 screw tapped into it.
4) 2* FCS grub screws to hold the front edges of your fin in.
