up to 150: Lightweight fabric, offers moderate shading, has high air permeability, but is sensitive to strong winds and rain.
from 151 to 300: Balanced weight, offers good shading, has moderate air permeability, and can be treated to be water-repellent for resistance to light rain.
Over 300: Heavy fabric, offers almost complete shading, has low to zero air permeability, and is resistant to rain and wind, especially if it has a PVC/PU coating.