Normally I wear US size 9.5-10, for Endorphin speed 2 (and Pro2) I ordered size 10.5 which fits perfectly for me.I like Endorphin shoes the most because it is very light and comfortable and responsive with good support, They are pushing runner forward while running and I run 40+ miles every week and most time now I am running with Saucony Endorphin shoes!it is the best running shoe I ever wore and I like it so much that I bought 3 more pairs of different color endorphin speed 2 ( Also along with 2 pairs of carbon-plated endorphin pro 2 for faster racing) .I will try Endorphin speed 3 / pro 3 for sure when there is a good price.