We took this mug on a beautiful hike up the Cascade Falls in Virginia. It didn't disappoint! The insulated Flip Lid will not spill when properly sealed, check out the video! The stainless steel tumbler’s double-walled insulation prevents sweating and keeps your drink at its optimum temperature for hours. Hot drinks stay hot for two hours, and cold drinks remain cold for eight hours. Hand wash only. The lid can be washed in the top rack of a dishwasher.