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.  The low profile t nuts can be used in some foils that use M6 t-nuts as they are the same low profile.  These are low profile meaning they are thinner than stock brass T-nuts by about 2.2mm from top to bottom but STRONGER.  See the video below for some of the testing including breaking T-nuts in slow motion.  Sold each.

This is the dimensions of this part:

These are also available in M6 on a separate product listing.