C/6 diagonal
c/6 diagonal is a diagonal speed that is equivalent to one sixth of the speed of light.
Spaceships

On September 17, 2005 Nicolay Beluchenko discovered the first c/6 diagonal spaceship, the seal. Beluchenko then discovered a tagalong for this spaceship on September 22, 2005.[1] These are currently the only known spaceships of this speed.
Puffers
No c/6 diagonal puffer technology is currently known.