The X stands for tenthe number of revisions Asics has made to this lightweight standard bearer. Serious racers will still find Asics's proprietary gel cushioning and the firm arch post they've come to depend on. But with an open-air mesh upper, this year's DS offers a more stable ride, a more breathable fit, and not an ounce more in weight.Bonus:
The shoe is covered, front to back, with reflective fabric; drivers will spot you a mile away.Bummer:
The DS old-school lacing system could do with a little Kevlar upgrade.