Hi Troels, With the recent support for dynamically optimising a R1 parameter the 'No Rex R1rho off res R1 fit' model has been merged into 'No Rex R1rho off res'. To extend on this, I think that the 'No Rex R1rho off res' model can be merged into 'No Rex'. That way, when the user chooses the 'No Rex' model, it will be automatically determined if the fit will be on-resonance or off-resonance, hence requiring R1, and if R1 will be fixed or optimised. So everything will be automatic. The aim is to minimise what we present to the user. A single 'No Rex' model is easy to understand - it is simply that no chemical exchange process is present. This is independent of whether the data is on-resonance or off-resonance or if the R1 parameter is fixed or optimised for the off-resonance case. Note I am deliberately not using CPMG vs. R1rho for this distinction as off-resonance fitting of a R1 parameter for CPMG data will be a future feature, as is supported in CATIA. What do you think? I have most of the changes now in place for this, but have not committed it yet. Regards, Edward