I missed this response earlier for some reason. Regardless, this would be appropriate for Columbus Aelle if it is metric tubing (i.e. 28.0mm seat tube outer diameter) but in the range for a lightweight hi-tensile steel if it's imperial tubing (i.e. 28.6mm seat tube outer diameter). I'm not sure when Mercier switched but most French manufactured changed tubing standards in the mid-1980s, which looks to be about the frame's age, so it could go either way.