Represent American Alpine Institute! The Nalgene Ultralight HDPE Wide Mouth bottle is very light (3.75 ounces) and BPA free. The wide mouth opening is compatible with many filters and accessories and makes cleaning or adding ice easy. The 63 mm loop top closure is leak proof and stays attached to the bottle. Graduations on the side to help you gauge your intake. HDPE bottles are dishwasher safe (away from the heating element) and have a wide temperature tolerance.