I can say with supreme confidence that (1) These are the best running shoes ever, on par with the obsolete Wave Maverick's (2) The lightness & extra stiffness has helped to heal & prevent injuries, particularly calf & achillies (3) they repeatedly shave between 10 & 22 seconds per mile vs. all other shoe brands and models - which is HUGE at races from 10K to marathons (4) they are significantly be