Having had every Ember lid I have owned fail within a few weeks or months, I decided to make something more resilient and something that would last. 
I was using my mug without a lid for a long time and when drinking any product with milk, a skin would form. The mug was harder to clean and the battery lasted half as long. With this new lid, all of these problems are solved and my drink stays warm longer, and is easier to drink.
Dishwasher safe and limits spills.
Made from high quality food safe ABS plastic, with a sturdy O-ring to seal the lid when closed.
Prevents milk-based drinks from forming a skin when left untouched for a while.
Doubles the battery life when compared to no use of lid.
Original mugs can spray hot liquid when opened and these lids won't do that.
Compatible with 2nd gen mugs only.