In brief, the (new) SI will be the system of units in which:
the ground state hyperfine splitting frequency of the caesium 133 atom capital Deltanu(133Cs)hfs is exactly 9 192 631 770 hertz,
the speed of light in vacuum c is exactly 299 792 458 metre per second,
the Planck constant h is exactly 6.626 06X x 10–34 joule second,
the elementary charge e is exactly 1.602 17X x 10–19 coulomb,
the Boltzmann constant kB is exactly 1.380 6X x 10–23 joule per kelvin,
the Avogadro constant NA is exactly 6.022 14X x 1023 reciprocal mole,
the luminous efficacy Kcd of monochromatic radiation of frequency 540 x 1012 Hz is exactly 683 lumen per watt,