Hands free technology - slip on and off. I wore to work once and you cannot return if worn. They just aren't for me :) Which makes a bargain for you!!! From Website: Comfort + sustainability? Yeah, we did that! The Madrid is fashioned with an environmentally friendly knit upper made from 100% recycled plastic bottles. It’s got a four-way stretch that makes it breathable (goodbye, sweaty feet!) We call it Eco-Knit. You’ll call it your new favorite shoe.