Which part of the climbing shoes stretch?

The part of climbing shoes that stretches is typically the upper material. This is the part that covers the top of your foot and is responsible for providing a snug fit. The upper material of climbing shoes is often made of synthetic or leather materials, which have some elasticity. When you wear climbing shoes, especially during extended use, the upper material can gradually stretch to conform to the shape of your foot. This allows for increased comfort and improved performance while climbing. It's worth noting that not all climbing shoes stretch to the same extent, as it depends on the specific design and materials used by different manufacturers. Nonetheless, the upper part of climbing shoes is the primary area that tends to stretch over time.