All the Dog Waterers use the same size lid. There are two versions of this lid. The standard lid that you received with your order and an identical lid that also has a purge hole and plug that you can see in this image. Why a lid with the purge hole and plug? With the Critter Cooler, occasionally some customers will find the lid difficult to open. This can occur when the air and water temperature change and increase the vacuum inside the container, we call this "lid-lock". With the lid and purge hole, you can release the pressure inside the container making it much easier to open. So if this happens to you, AND you contact us within 60 days of your order date, we will send at no charge the lid with the purge hole. Don't order on line, you need to call us and leave a message at 877-6-BIG - DOG or email at Shampoo4Dogs.net.