US sizing The Challenger's previous nickname "ATR" stands for All Terrainand these really are incredibly versatile shoes. As is typical for Hoka, the Challenger also features generous cushioning. On the brands own cushioning scale, this model is rated as medium. The Challenger performs well on almost any surface, including hard ground. Its a shoe that nearly every runner can make use of! The Challenger is also easy to recommend for walking and light hiking in relatively easy terrain. Compared to version 7, this 8th edition has a larger drop (8 mm, previously 5 mm) and a grippier outsole pattern. - Neutral running feel - Heel-to-toe drop: 8 mm - CMEVA midsole for impact absorption - Outsole made with different rubber compounds to optimize weight and grip - Light toe protection - Lug height: 4 mm - Reflective details Check the size chart for instructions on how to measure foot length and choose your size based on the result.