Hi Peter, Thanks for the report. I've verified your findings that feffit() is doing the wrong thing for the Fourier transforms for data on grids other than k-grid of 0.05Ang^-1. Here's what is happening: feffit() really is interpolating data internally onto the 0.05 grid for the fit. The fit _should_ procede correctly for data on any grid. Anyway, at the end of feffit() command it sends the data off to the fftf() command to make the chir_mag, etc arrays. It is at this point that the k-array in ***NOT*** being sent to the FFT. I've verified in my own tests that including the k-array in the FFT works, giving the right FFT. hopefully I will get a fixed version posted this week. But currently, the r-space data (data only, not the fits) from feffit() are wrong when a non-0.05 k-grid is used. Simply doing fftf(real=data.chi, k = data.k) will give the correct r-space data. I also noticed another wart and small inconsistency between feffit() and fftf() from your example, which has the 'data' over a smaller range than the FFT window. Thanks, and sorry for the trouble, --Matt