The leak proof silicone seal on the flip cap ensures the bottle is well-sealed and no spill; the leakproof silicone ring in the cap ensures no side leakage; the self-sealing valve in the drinking mouth keeps fluid from leaking out, even when the bottle is upside down, when there is no squeezing on the bottle body. Besides, the stainless steel lock ring prevents the cap from accidently open. So, you can rest assured this water bottle will not leak.