need to have with every klean kanteen bottle,
Verified Purchase(What is this?)
This review is from: Klean Kanteen - Stainless Flat Cap (Kitchen & Home)
Classic Klean Kanteen bottle are sold with a sport cap, which is useful but not completely watertight (at east mine isn't). This cap allows to store safely the bottle in a backpack or similar even if it ends head over feet.