The 12 liter Adv Skin 12 Set has ample cargo space not only for your drinks but also energy gel, snacks and foul weather clothing. - Front panel bottle pockets include small item pockets - Two 500 ml Soft Flasks included - Large main compartment at rear - Compression straps - Compatible with 1.5 liter hydration reservoir - Telescopic and fold-away pole holders - Use your chest circumference to choose your size: - XXS: 76-81 cm - XS: 81-86 cm - S: 86-91 cm - M: 91-96 cm - L: 96-102 cm - XL: 102-110 cm Women's sizing. Choose the size as you would choose a women's tee shirt.