This headband is one size fits most and the size cannot be adjusted. The headband is sewn at a 6.5" diameter (13" circumference), keep in mind that measurement is before it stretches. The bow measures approximately 4.5" across. This style is secured with adhesive once tied and is not meant to be untied. The soft woven patterned material is a nylon/polyester/spandex blend, produced to our specifications, in the USA .