Summary: Good little product, but be careful about the listed size. The 3 1/2 " x 8" spec is for the **outer** measurements including the bottle. The included plastic bottle smells of plastic and you'll want to use a lexan bottle by you-know-who. :) Your 1 liter water bottle won't fit. The half liter bottle will, but that's pretty small.
Summary: The Tamrac bottle holder attaches nicely to your backpack and frees up your hands when hiking. Keeps the bottle snug in the holder, so if you bend over with the pack on your back the bottle stays put.