Nitrofoam: Advanced nitrogen-infused foam designed to provide superior responsiveness and cushioning in a lightweight package PumaGrip: Durable performance rubber compound designed for all-surface traction The upper of the shoes is made with at least 30% recycled materials. Discover a new era of support, guidance, and comfort for all runners with the Puma ForeverRun Nitro 2. This new and improved version provides unmatched stability thanks to a wider midsole, upgraded dual-density Nitrofoam cushioning, and an improved fit with a rolled collar and engineered knit upper. Made for your everyday running and training needs, ForeverRun Nitro 2 is a shoe that will make you feel like you can run forever.