Smoke Flow where is the set size option in panel?

Trying to follow a tutorial but a setting is missing in smoke flow panel, i set the flow source to particle system and the particle system to particlesettings but the set size option is not there and even the 2.8 official blender manual mention it is suppose to be there so what am i missing here guy’s?

I am not sure but i think they change the name in 2.80 to ‘‘particle size’’ but they didn’t update the documentation, i will wait for confirmation.