These are Replacement M6 Stainless Steel T-nuts and M6 x 25mm Mounting Screws for the any hydrofoil that uses the M6 T-nut including Takuma, Naish and others. These are hard to get replacements that we now have in stock. They are sold as a complete set.
Here are the total dimensions of the track nuts:
Track width: 8.5mm
Total width: 14.9mm
Total length: 23.9mm
Total height: 6.20mm
Mounting Screws are M6 x 25mm Socket Head Screws