[Pictured is the version without the VF cutout, this version has a cutout] This hood fits to the existing bayonet attachment via a very tight friction fit. On first fitting it may feel you are forcing it, but this is normal and the mount has been tested across 3 different examples.
This is a small hood for the Voigtlander 35mm f1.4 Nokton Classic, Voigtlander 40mm f1.4 Nokton Classic lens or Zeiss 50mm f2 Planar lens as a replacement for the £48-70 ones from the OEMs. It gives that rectangular hood look, instead of the circular metal one.
A version has been tested and is no problem on full frame as it's actually wider than it needs to be. As that/this version slightly intrudes into the viewfinder on a Leica M, this is the version with the cutout for those that would prefer one.
This hood is mainly for the "look" - please see my other hoods for more compact, taylored hoods for these 3 lenses.