Most portable cups use separate operations to lock and unlock the cups. However, people often forget to lock the cup after closing the lid. When carrying with it, they might unintentionally touch the button and unlock the cup, making the liquid spill all over the bag. The PS-REFRESH is self-locking and leak-proof, combining the two operations mentioned above into one. Press and slide, and then the lid is open; you could do it with just one hand. Press the button to close the lid, and the cup is automatically locked. With this design, you will never have to worry about the leaking of your cup.