Don't let the 9.6oz fool you - these shoes are engineered to move your body fast. The carbon plate, the stack height, the fitted upper, and air pockets all work in harmony to propel you forward for some splits that you wouldn't have expected. Note that people may find the front toe box a tight or constricted feel when first trying on the shoe, but after a brief break in period the shoe feels locked in. I have been able to run in my first pair to ~700K which includes running a 50K in 3:59, a 5K in 18:15, as well as a 1:23 TT half marathon before bursting an air pocket. Happy to have 2 more currently in rotation for my speedwork and tempos. They are a win!