What size mattress can the Ultra-Cool pad fit? August 11, 2020 20:14 The Ultra-Cool Pad can be used on mattresses that are 15 inches in height or shorter. Related articles Can I wash my Ultra-Cool Pad? How long will it take for my order to arrive? Can I use a bed frame with my new Adjustable Base? How do I use the Adjustable Base with a King or California King mattress? How deep is the fitted sheet?