Weight 15 oz / 430 g
Capacity 250 cu in / 4 L

Where to Buy

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Manufacturer's Description

Visit Osprey's Viper 4 page.

Retailers' Descriptions

Here's what other sites are saying:

The lightest of the Viper series, the Ospery Viper 4 pack provides a 2 liter HydraformTM reservoir, a heat embossed fabric pocket for carrying small items and a bungee lacing system on the front panel for securing an extra layer of clothing.

- CampSaver.com

Built for recreational mountain biking, trail running, and day hiking, the lightweight Viper 4 Hydration Pack from Osprey features a stretch harness, ventilated back panel, and 2-liter reservoir.


Streamlined and sleek, the Viper series from Osprey is ready for mountain biking, hiking and trail running. These specialized packs use Spacer Mesh back panels to move moisture, and a Biostretch harness to move with you on aerobic routes.

- Mountain Gear

Hit the trail prepared when you head out with the Osprey Viper 4 Hydration Pack. This hands-free hydration system stores up to two liters of water and can tote the other essentials youll need during your trail runs, rides, and hikes.HydraForm reservoir is made with BPA- and PVC-free materials and features a design that squeezes your water supply for easier drinking SpacerMesh back panel provides super-light cushioning for a comfortable fit BioStretch shoulder harness system features mesh-covered foam for superior comfort and small sleeves to hold your energy gel pouches LidLock helmet clip feature allows you to attach your bike helmet to your pack for hands-free storage. Rear bungee system helps reduce pack volume if youre carrying a smaller load Reflective detailing on front panel and a blinker-light attachment loop help keep you visible

- Backcountry.com