It’s a custom-made medical arc.

The insole is the inside part of the shoe that runs underneath and supports the bottom of the foot. Insoles are also referred to as footbeds and inner soles. They are usually easily removed. People often replace the original insoles with a pair of specialty insoles they’ve purchased separately for a more comfortable and supportive fit. .

The insole attaches to the upper part of the shoe and is often made of cellulose paperboard or a synthetic insole board. Specialty insoles can be added to make the shoe more comfortable, control odor and moisture, and absorb shock. For health-related reasons, orthotic insoles can better position and support the foot.