I recently bought a 3 x 4 imperial 16mm hole Sigmund. What’s interesting is that measuring the diameter of the spigots on the bottom of 5/8” and 16mm rated fixtures shows that they’re the same. My 5/8” BuildPro fixtures are the same as the 16mm fixtures from Sigmund. So when buying any fixturing devices for these tables, don’t worry if they say 5/8” or 16mm. They’re fine either way. Just buy the ones you like best.