These are low profile replacement M8 Stainless Steel T-nuts for the any hydrofoil that uses the M8 T-nut, which just about all Tracked hydrofoils, including Naish. These are low profile foil track T-nuts, meaning they are thinner than stock brass T-nuts by about 2.2mm from top to bottom but STRONGER.
These are also available in M6 on a separate product listing.