Since all three Pauli matrices are present, there is no further Pauli matrix that could open a gap in the spectrum and Weyl points are therefore topologically protected. Tilting of the linear cones so the Dirac velocity varies leads to type II Weyl semimetals. One distinct, experimentally observable feature of Weyl semimetals is that the surface states form Fermi arcs since the Fermi surface does not form a closed loop.