The Crater Dot is a comfortable lounge for your pet. The polyester plush dot center provides an easy to clean and comfy spot to relax. The foam lounge base is polyester fabric over a moulded foam form that is contoured to provide just the right padding for you pet. The Sleepypod Warmer Kit can be installed in the pocket in the base. You can use either size Warmer Kit, but we recommend the medium size as it will warm the entire plush area.