Nike Air Zoom Vapor X Knit Women's Tennis Shoes Opti Yellow/Valerian Blue : The Nike Zoom Vapor X Knit hard court tennis shoes feature the latest technology made for tennis. This model features reliable cushioning from the Nike Zoom Air unit. The knit upper adds a modern twist while providing lightweight, breathable support for powerful, explosive movements between shots. Shoe Technology Upper: A circular-knit material is lightweight and breathable. High-strength yarns provide support during movements on the court. Midsole: Soft foam midsole with Zoom Air unit in the heel offers low-profile responsive cushioning. A stretchy internal sleeve hugs the foot for a sock-like it. Outsole: Rubber outsole with XDR compound on the heel and forefoot provide multi-surface traction and durability. A pattern of small triangles on the outsole adds durability to high wear areas.