Made of thick elastic material. They are warm without burning the foot. Pleasant feel. Good for workouts. They stay in place, they don't fall off. Their height is lower than it appears in the photo.

edit- one year later, with frequent use, the heels started to wear out. I believe they lasted about as long as the Nike/Adidas sports ones. If you want something more durable, then I would suggest going for thick/long ones from the army or hunting.