I bought the Hydration pack with the insulation so that I wouldn't have to worry about it freezing on me. Well if you wear it outside of your jacket the water will freeze in the tube, but if you wear it under your jacket you want have anything to worry about.

The size is perfect. Small enough that you're not carrying around a ton of extra weight, but big enough to keep you hydrated for a day. The insulated tube will make for a good snowboarding trip, but haven't tried that yet. It's only downfall is that it's hard to dry out after use. It has a seam on the inside that makes drying difficult. But overall a good buy.

Works great in all winter temps until about 20 degrees. Bite valve is nice, sits snug to your back and you get plenty of suction out of it. Great bag until it freezes, so use it in mild winter climates.

I bought this after skiing a season with the Rim Runner from CamelBak, which was too big, especially when you land on your back and get whiplash. The Zoid is small enough to fit under my ski parka, yet still holds plenty of water and the little pocket holds my keys, powerbar etc. You don't have to sit sideways on ski lifts with it either, water stays just the right temp. and the mouth tube never freezes.