The Inov8 All Terrain Pro Vest 0-15 is two packs in one. It is a stripped back race vest, which has an additional 15 litre back pack for longer training runs where more capacity is needed. The pack is ultra-secure as it is attached through six compression straps, ensuring zero bounce. EXCELLENT VERSATILITY Both a race day vest and a 15 litre pack. HYDRATION OPTIONS You can either run with the two supplied 500ml soft flasks with tube in the front pockets, or add a reservoir in the back pocket. QUICK ACCESS AND EASY TO USE The item has multiple pockets. If used as a race vest, it has eight pockets, and an additional three if the pack is attached as well. They are all easily accessible. SIZING (Chest Measurement) S/M - 86-96cm M/L - 96-106cm L/XL - 106-116cm