Ratio to CT14  predictions of the production of muons from W$^-$ (top) and W$^+$ (bottom) decays measured in p-Pb collisions at $\sqrt{s_{\rm NN}}=8.16$ TeV by the ALICE and CMS  Collaborations. The measured ratio is compared to the one obtained from pQCD calculations with CT14+EPPS16 . All the calculations include the isospin effect. The grey band around the line at unity indicates the uncertainty on the calculations with CT14 PDFs.