Mizuno Running - Wave Spacer (White/Red/Black) - Women's: Developed for the runner who believes less is more. 20mm/10mm (heel to forefoot ratio). Composite Wave(tm) in a fan-shaped configuration that utilizes two distinctly different materials for specific cushioning upon impact and support throughout the gait cycle. The lateral side of the Wave(R) plate is made of rubber for excellent cushioning at heel strike, while the medial side of the plate is made of pebax for performance support. AP midsole for lightweight, repsonsive cushioning. X-10(tm) in the heel for durability. Solid rubber in the forefoot for durability and flexibility. Shoe weighs 7.6 ounces.