Product Story Named For The Woman-Specific Double X Chromosome Dna Sequence, The Run XX Nitro Stands Behind Puma's Run For Her Motto With A Progressive, Female-Specific Design. Featuring An Updated Fit That Hugs A Women's Foot At The Heel, Instep, And Arch, The Running Shoes New, Firmer Durometer Nitro Foam Midsole Is The Perfect Balance Of Durable And Lightweight. Run Guide Promotes Proper Alignment And Increased Stability For Longer Distances. Features & Benefits Nitro : Advanced Foam Technology Providing Superior Responsiveness And Cushioning In A Lightweight Package Run Guide: Firm Density Guide Rail Designed To Keep Your Foot Aligned And Centred Through Each Stride. Details Low Boot Construction Mesh Upper Nitro Foam Midsole Puma Grip High-Traction Rubber Outsole Mesh Tongue Lace Closure Puma Cat Logo On Toe And Heel Puma Formstrip At Medial Side.