All SHRED. goggles are designed to fit in any SHRED. helmets. However, the best fit is achieved when you select a goggle model that corresponds with the size of your helmet. For example, the Amazify goggle fits in all helmets (size small to XL), but they fit best in medium and large helmets. There is a sizing chart at the bottom of each goggle model page that has information on which helmet size the goggle fits best in.