What do the model numbers mean? Scott T. August 31, 2018 17:04 Updated The model or style number is a naming system for our shoes. While most of our "higher-numbered" styles feature more technology than our "lower-numbered" shoes, that is not always the case. When deciding on a particular shoe, both the intended use of the shoe and your individual needs should be considered. The full model number, which is broken down into 3 parts, can be located on the underside of the tongue. The letters before the number designate the gender and the activity for which the shoe was designed, as follows: MT = Men's TrailWT = Women's TrailMO = Men's Outdoor/Multi-sportWO = Women's Outdoor/Multi-sportMW = Men's WalkingWW = Women's WalkingMX = Men's Cross-TrainingWX = Women's Cross-TrainingMC = Men's TennisWC = Women's TennisKJ = Kid's RunningKV = Kid's Running with hook and loop closure systemKT = Kid's TennisKX = Kid's Cross-TrainingRC = Racing/CompetitiveUS = Made in the USAThe last two digits in a running shoe's style number specify the type of shoe as shown below: 40 (Optimal Control)*: Shoes in this category provide superior control, stability, cushioning and support for biomechanical needs, such as pronation or low arches (eg, 840, 1540). *With the exception of the 840v4 running & 840v2 walking. These styles are neutral cushion styles. 50 (Fitness Running): For training on roads or for indoor workouts, the 50 series offers the combination of visual attitude and innovation with the responsiveness and power athletes need.60 (Stability): Designs that offer industry-leading stability to reduce pronation while also providing unparalleled cushioning and comfort (eg, 860).70 (Light Stability): The perfect combination of stability and speed, all in a lighter, sleek profile designed for runners who train at a faster pace (eg, 770).80 (Neutral): For high-mileage runners who require light shoes and the protection of superior cushioning (eg, 980, 1080).90 (Speed)*: For faster runners who want every advantage, including a superior ride and fit. The choice styles for professional and nonprofessional speed and distance runners (ie, 890). *With the exception of the 990v4 and its predecessors. The letters after the numbers generally indicate the major colors of the shoe. For example, WB indicates white and blue and BK indicates black. A number following after is the version number.