I've been using the Crono Mk1 in non-UCI races. It was also a very fast shoe, However the shape was long and it could cause some resistance depending on the pedaling angle (the laces were good, though). After using the Mk2, I felt it was lighter, fit better, and had a larger allowable pedaling angle. The aero cover seals perfectly, and of course there is no need for heavy, hot shoe covers. I was able to win my age group in the 100km TT . https://www.instagram.com/p/CMytEQwjZsO/ Thank you very much.