This Klean Kanteen cap is spill-proof and creates a 100% safe environment for your drink in the mug. The lid is made of 18/8 food grade stainless steel, including threads, so your drink never comes in contact with plastic. The replaceable caps are easy to change so that they can be used all day long, from morning coffee, afternoon smoothie, water to the gym to a beer in the evening. Dishwasher safe. Compatible with Wide Klean Kanteen thermo mugs.