Nathan Vapor Airess Race Vest Hydration Pack, 9-Liter, Small/Medium, Sparkling Cosmo NOTE:This product is intended to be close-fitting for the best stability and running performance. If your measurements are close to the maximum chest sizing, we recommend to size up for flexibility.Designed specifically to fit the female form. Over the shoulder load lifters keep water and gear close to the body for maximum no bounce comfort Body mapped, super breathable materials for maximum comfort Equipped with a 2L bladder with quick release valve Two easy access front bottle pockets and front right stretch mesh stash pocket holds several gels Size: XS (28" to 33" / 71.1 cm to 83.8 cm in chest) Size: S/M (31" to 36" / 78.7 cm to 91.4 cm in chest) Size: L/XL (34" to 40" / 86.4 cm / 101.6 cm in chest