The insoles are made of pure felt. Top and bottom are identical, ie they can be used on both sides. They are thick enough (about 5 mm) to cushion the step pleasantly. The heels of the shoes should not be too flat, or it could happen due to the thickness of the soles that you do not have sufficient grip more with the hoes in your shoes and slip back. The soles are generously proportioned so that they are easily also may reduce in width and length with narrow shoes. It is not necessary that the soles to order one size bigger. I would buy me at any time.