Which bolts and nuts to use to install Osymetric chainrings to replace Shimano Ultegra R8000 chainrings?
Shimano 46 tooth outer chainrings are flat and lack the '3d' profile of the 50 and 52 tooth rings. The 'fancy' bolts you linked to are shaped to cap off the crank spider arms. Those will work with the flat Osymetric rings.
Regular bolts will also work but not look as 'finished'.