These are extra stainless steel M8 bolts for your hydrofoil setup.  Available in Torx T40 or Philips drive. 

These are all countersunk flat head Stainless Metric Bolts in various sizes.  We can tell you what size you need for most foil setups.  The best way to do it is to measure the bolts you need from the ones that are already on your foil. Use the graphic below.