Diffusion imaging derived in-vivo estimates of axonal microstructure have great potential as clinical biomarkers in various neurological diseases, but current approaches suffer from long scan times and infeasible hardware requirements. In this study we demonstrate a novel imaging protocol that achieves high-resolution in-vivo axon diameter estimates in the corpus callosum in only 35 minutes of scan time. We show agreement of our estimates with reported histological assessment of the corpus callosum and show good intra- and inter-subject reproducibility in 5 healthy subjects.