I bought the 3.5mm polyester replacement insoles for both pair of my Nine2Five shoes, as both of them are about 3 years old. The shoes themselves are in very good shape, but the insoles had become flatter with time and wear. The replacement insoles are perfect; the same as the original insoles and they make the shoes as comfortable to wear as they were when they were new. If you aren't ready to replace your shoes, a new pair of replacement insoles might work for you too!