It has been shown that reflectivity experiments can be carried out with an in-house diffractometer with high performance and advanced resolution. This is especially true for an analysis of the hydrophobic membrane thickness variation upon peptide insertion. For a labeling approach, presented herein, in-house reflectivity holds the advantage of a higher contrast variation compared to energy variation around the I-L III absorption edge but includes the application of nonisomorphic samples. However, in-house reflectivity in combination with heavy-atom labeling is generally suited to generate reliable results for peptide side-chain positioning within the lipid bilayer (Küsel et al. 2007; .