WE USE ETPU (ENGINEERING THERMOPLASTIC POLYURETHANE ELASTOMER) FOR THE SOLES OF OUR APX RUNNER. THIS LIGHT AND ADVANCED MATERIAL IS COMPOSED OF 70% AMORPHOUS RESINS FOR STRENGTH AND DIMENSIONAL STABILITY, AND 30% CRYSTALLINE RESINS FOR WEAR RESISTANCE. ETPU ENSURES THE APX SOLES ARE DURABLE, IMPACT-RESISTANT, AND OFFER SUPERIOR PERFORMANCE FOR RUNNERS. THE ETPU SOLES ALSO ENHANCE COMFORT AND ENERGY RETURN, MAKING THEM IDEAL FOR SHORT-DISTANCE AND HIGH-INTENSITY RUNNING.