As the name implies, the Viper 13 features 13-liters of storage, which is an excellent size for day hike, long trail run or a mountain bike ride. The pack weighs just 1 pound, 6 ounces (.62 kg) but features Osprey's trademark high quality construction which makes it feel like it is tough enough to take any abuse you can throw at it. That is much appreciated when you start putting the Viper through its paces on the trail.
Despite its narrow shoulder straps, this pack is quite comfortable to wear, even for extended periods of time. Thin waist and sternum belts allow the wearer to quickly and easily dial in a solid fit and once locked into place, the Viper doesn't shift around while moving. This is a great quality to have no matter how you're using the pack, but it was especially appreciated while trail running. The back of this pack is designed to help facilitate some ventilation in an attempt to keep us cooler while being active, and while it is effective to a degree, it is difficult to integrate a true ventilation system in a pack of this size.
In terms of storage options, the Viper is well equipped to carry all of your gear. The main compartment is fairly spacious with a couple of organizational slots. A secondary pocket includes a key clip and several mesh pockets for keeping your important items close at hand, while a mesh pocket on the front of the pack is great for carrying an extra pair of shoes or some other items you need easy access to. There is even a stash pocket on top that is lined with soft fabrics to protect sunglasses, a smartphone or some other delicate items. There's even a built-in lidlock for carrying a bike helmet for your two-wheeled outings. In short, no matter where your day trip takes you, this compact pack can carry just about anything and everything you might need for your adventures.
As mentioned, the Viper is a full featured hydration pack and Osprey ships it with a 3-liter bladder. That bladder is cleverly stored in it's own compartment and puts plenty of water at your disposal. In another nice touch, the bite valve on the bladder features a magnetic clip that attaches to another magnet on the sternum strap. That keeps the water tube out of the way until you need it and the magnet is strong enough that the valve doesn't shake loose when your activity gets more vigorous.
When put to the test in the field, the Viper performs as well as I had hoped. It offers a good fit, sits well on my torso and provides lots of carrying capacity for a solid day on the trail. The hydration system is easy to access, takes no time to fill and provides plenty of water when needed. Osprey has delivered another excellent pack for mutlisport athletes. It is comfortable, versatile and built to withstand the punishment of the trail. What more could you ask for out of a lightweight pack that is just as useful on a mountain bike as it is on foot?
With a price tag of $109, the Viper provides a lot of performance for the price. If you're in the market for a new pack for all of your outdoor activities, it is tough to beat the Viper, which is also available in 10, 7 and 4-liter models as well.
