The Nike Kukini Free: Flexible Slip-On Comfort The Nike Kukini Free Women's Shoe Delivers Complete Comfort In A Slip-On Design To Help Strengthen Foot Muscles With Every Stride. It Offers A Barefoot-Like Feel With Breathable Stretch Fabric In The Upper & An Outsole That Allows For Natural Movement. Benefits Flex Grooves In The Outsole For A More Natural Stride Skeletal Rubber Webbing On The Upper For Added Support Laceless Neoprene Mesh Upper For Lightweight Breathability Durable Phylite Midsole With Nike Free Flex Grooves For Cushioning & A Barefoot-Like Feel Design The Nike Kukini Free Is Inspired By A Tri-Athlete's Need For A Lightweight Shoe That's Easy To Take On & Off, With A Unique Webbed Cage That Provides Comfort & Lockdown Without Laces. High-Wear Areas On The Outsole Are Reinforced With Tough Carbon Rubber To Increase Durability. Comfort The Stretchy & Breathable Dynamic Fit Upper Provides A Well-Ventilated, Lightweight & Remarkably Comfortable Fit. Flex Grooves Along The Length & Width Of The Outsole Enhance Flexibility & Help Maintain Stability. Origins After Learning That Stanford Athletes Had Been Training Barefoot On The University's Golf Course, Three Of Nike's Most Innovative & Creative Employees Set Out To Develop A Shoe That Felt Natural & Weightless, Similar To Bare Feet. In 2002, They Examined A Group Of Men & Women With Pressure-Measuring Insoles Taped To Their Feet, Using High-Speed Cameras To Capture Images Of Each Foot In Motion. The Team Spent Eight Years Studying The Biomechanics Of Shoeless Running. The Results Yielded A Profound Understanding Of The Foot's Natural Landing Angle, Pressure & Toe Position, Allowing Nike Designers To Build An Unconventional & Flexible Running Shoe From The Inside Out.