Example of inversion results. The black and red curves show the observed and inverted profiles, respectively. The two sets of profiles correspond to the limb-side penumbra. Left: TIP, right: GFPI. The horizontal lines in Q,U,V panels mark the zero and  ± 3   σ noise levels. The GFPI profiles are filtered (cf. Sect. 2.2). The selected inversion setup only produces symmetric profiles, causing the imperfect fit of the e.g., Stokes-I and V of both instruments (Sect. 3.2).