The Hydrastash system is engineered to use your body’s heat to keep the microbite valve from freezing. You can actually keep your microbite valve completely out of the elements and get water from the system without unzipping your jacket by just turning your head down and drinking from the microbite valve. The upright design of the Hydrastash system also aids in reducing freezing. While most hydration systems hang over your shoulders leaving the residual water all the way up to the bite valve, which is at a lower height than the tube on your shoulder. This water can freeze in your exposed tube/valve. In the Hydrastash system, the upright design allows the residual water to flow back down the tube, further reducing the possibility of freezing.