Simple sketch of two plausible configurations of circumstellar matter in HMXBs. On the left side, X-rays are transmitted through a dense medium (e.g. the strong wind of the donor), producing high N_H directly correlated with the EW of FeKα. On the right side, X-rays are reflected in an accretion disk producing fluorescence and also transmitted through a more diffuse medium. In this case N_H is not necessarily correlated with the EW of FeKα.