Finally, to demonstrate that 10 nM measurements can be recorded to sufficient quality, we averaged a vtRIDME experiment of the 10 nM GB1 sample for approximately 60 h, our internal maximum averaging time used for previous sensitivity benchmarking, which yielded clearly visible oscillations, and a modulation-to-noise ratio of 12.5 (Figure ). While this is below the recent recommendation of a modulation-to-noise ratio of at least 20, this data is still of sufficient quality to provide useful structural restraints. An attempt to further lower the concentration to 5 nM protein concentration for a vtRIDME measurement turned out to be beyond our current sensitivity limit and was considered unsuitable for processing (Figure ). In summary, we show that combining CuNTA-SLIM spin-labelling with vtRIDME can significantly enhance PDS sensitivity by almost an order of magnitude compared to established procedures (i.e., ctRIDME measurement of CuNTA-nitroxide labelled protein) reaching a concentration limit of 10 nM in the distance range of 3 nm. It is expected that longer distances and broader or more complex distributions will require longer dipolar evolution times or better modulation-to-noise ratio. This would likely demand higher concentrations than achieved here.