I can generally comfortably fit any bike from 53-56 cm with typical adjustments at the seat/seat-post and stem. I'm 5'8 with a 31 inch inseam. I prefer the longer end of my size range, because I find that the shorter frames put me in a less aerodynamic, more upright riding position. The 4 bikes I mainly ride are all 55 or 56 size at the seat tube, center of bb to top of top tube.