For Today Only Woot! is offering the High Sierra 53733 Piranha 10L Hydration Pack for only $29.99. This is 70% off the list price of $100, and they're selling for at least $42 at Amazon, depending on the model.

The packs have received high reviews, and they are quite useful for hiking and outdoor sports. The system is BPA free and antimicrobial. Have fun at any temperature with an insulated hose that won't easily freeze in cold climates.