Rubber sole A flat, wide heel creates a stable base when you're lifting. A softer foam core cushions your foot, while a firmer outer layer is durable and supportive. The lightweight design includes durable mesh to keep your feet cool and comfortable. Pull tabs at the heel and tongue The Nike Free Metcon 3 combines Nike Free flexibility around the forefoot with Metcon stability in the heel to help you get the most out of your training session.