Hydro Flask Standard Mouth Loop Cap is designed for everyday use as well as challenging outdoor environments. It provides a leak proof seal, which aids in keeping your Hydro Flask contents cold or hot. Clip to a backpack or messenger bag and take your bottle on the road.For Hydroflask standard mouth Bottles (Campmor Item #80302 and #80303.). Also fits other standard mouth bottles with 1.875" opening. Leak proof seal. Loop top to clip to backpack or messenger bag. Made from polypropylene. BPA free.