Features Enter your model number to make sure this fits. Lightweight Construction - Formed from lightwieght rips stop fabric and stretch mesh construction. Adjustable shoulder strap - Contoured with a mesh back and fully adjustable to provide a highly comfortable fit. Antidote® Reservoir - One of the best on the market with a multitude of features. Adjustable Harness and Pockets - Accommodating for a range of storage. Stretch Cargo Pockets - Provides convenient storage and quick, easy access. Description Product Description Camelbak's most versatile vest features expandable storage to accommodate gear for varying conditions and distances. It's got 2 litres of hydration capacity, a sweat-proof storage compartments for your keys and phone, and a stretch mesh pocket for gels or salt tabs. The external-fill feature also lets your refill your reservoir without removing it from the pack, so you can save time on the trail. Worried that the weather might turn on you? The stretch mesh compartment expands to hold an extra layer or two. Need more than 2 litres of water? Load up the chest pockets with two extra bottles. And with two sternum straps and a hook-and-loop adjustable harness, this pack stays put now matter how rough the terrain. Key features of the Ultra 4 include Adjustable harness with cargo pockets expandable cargo compartment Sweat-proof phone pocket Expandable cargo compartment 2 Litre Hydration The Pack Designed from the ground up to provide lightweight hydration and adjustable storage to tackle the most demanding of terrain. The main body features rip stop fabric yielding a durable and weather resistant embodiment, parred with integrated mesh throughout the Marathoner is exceptionally lightweight and comfortable to wear. The contoured shoulder straps and adjustable sternum straps create a fully adaptable and adjustable fit, that moves with the wearer rather than against. This design reduces the amount of bounce and feedback from the pack whilst the wearer transitions through various motions and activities, crating a highly comfortable fit that won't impede its wearer. Two cargo pocket at the front offer generous room to store and easily access items, along with a zip locking sweat proof pocket and multiple lash points. This allows for a number of storage combinations that means you can stash more than you may think with the Ultra 10. The Antidote® Reservoir The reservoir used in the Ultra 4 is of a standard and quality expected from a brand with over 20 years experience. The