Babolat's most innovative tennis shoe takes another big step forward with the introduction of the Propulse 4. This update to the Propulse line has a few new performance features while maintaining the same great stability, durability and fast feel that we've grown to love from the line. A major update is the use of Babolat's new Side 2 Side propulsion technology in the midsole, designed to provide exceptional court response and a power boost with every step. You continue to get a customized fit as well as optimal support with the FootBelt straps on the heel and upper of the shoe. The Cell Shield that wraps the upper offers durability and support, and the Michelin OCS2 outsole is backed by a six month outsole durability guarantee.