[Ti/Zn] vs. [Zn/H]. In contrast to Ti, the portion of Zn, which is depleted into dust grains can be expected to be comparatively small. Therefore [Ti/Zn] can be treated as a good indicator of dust depletion. Also because of this [Zn/H] is a good indicator for the metallicity of the observed system. This plot shows that on average dust depletion is more severe in systems with higher metallicity.