This topper is hand made from scratch, using traditional millinery techniques, so I can make it to fit. I make a hat base from buckram, a fabric that is stiffened with glue, then sew on millinery wire around the crown and brim for extra strength. I pad the base with fleece mull, then stretch and sew the outer fabric into place. The hat is fully lined and has a grosgrain sweatband. It measures approximately 5 1/2" high in the crown, by 12" front to back across the brim, though these measurements will vary slightly dependent on hat size. To measure your hat size, simply use a tape to measure around your head just above the ears (Inches or centimeters, I don't mind). If I need to make one up, please allow 2 weeks. This hat is currently made up in medium, approx 23"