The term "leak-proof" applies to Thermo Scientific Nalgene products that meet the following criteria: a) For bottle/flask/funnel seals with cap sizes less than 100mm When the system is filled with water, invert it for two minutes at an atmospheric pressure of 2 psig, and the water inside will not overflow; b) For bottle/funnel/flask sealing systems with a cap size greater than 100mm, after filling it with water, invert it for 15 minutes, the water inside will not overflow. Note: If other liquids are used for the above test, different results may be obtained. To ensure safe use, customers are advised to test Thermo Scientific Nalgene bottles and closures under planned application conditions. Thermo Scientific Nalgene products are leak-proof when used with Nalgene sealing caps at room temperature and pressure.