I have now had 3 pairs of FiveFingers. The Bikila I bought (E41 size) 5 years ago were just great. Earlier this year I bought a black KSO pair which were 1 size up on the Bikila E42 but were too tight. So I tried again, and got these blue FiveFingers a size up again E43, and they fit great. I leave the shoe lace as loose as it can go; they are not too loose. So now I am using FiveFingers which are 2 sizes up on my original Bikilas. The Bikilas still fit, as do these new ones. I don't like the KSOs.