In my expierience Fizik runs larger than Shimano. In Shimano I found a 45 too small. I currently wear a 45 in Fizik with an orthotic- a little long but I can wear them all day in comfort. Fiziks look great long term- just dont look as beat up as some of the others over time. S-Works are the worse for wear- great shoe but finish is gone in no time, eg toe-overlap.