Description:Material:' These leak-proof lids are made of lightweight, durable plastic, provide a good seal, are safe for use with your cups, and are dishwasher safe.Leak-proof design:' The replacement lid features a great quality sealing design, with a sealing silicone O-ring and an open design to effectively prevent liquid spills and splashes. The lid' s excellent airtightness keeps beverages at low or high temperatures.Easy to use:' Simply slide the button to easily replace the lid, allowing you to choose between drinking directly or using a straw. This lid works perfectly with the Stanley 40oz insulated mug, easily replacing the original lid without replacing the entire mug.Versatile: Great for home, office, travel, or outdoor activities such as picnics. It effectively prevents spills and dust from getting in, making it perfect for carrying coffee, tea, or other beverages.Note: To avoid purchasing an incorrectly sized lid, please measure the inner and outer diameters of your cup before purchasing.