Ion mobility spectrometry provides an additional dimension that separates ions based on their size and shape in the gas phase. The measured ion mobility can be used to derive a collisional cross section (CCS), which intrinsically depends on the ion structure. Interestingly, isobaric and isomeric peptide sequences can potentially be distinguished by their different CCS . The difference between the observed and the predicted CCS can be used similarly as ΔRT. A few pipelines support the use of ion mobility features . As ion mobility becomes more prevalent on modern instruments, ion mobility-based features will become more common.