Sleep soundly on the Casper Nova Hybrid Mattress. The Nova Hybrid provides support where you need it most with the luxurious plushness you crave. Available in 6 sizes. A luxuriously soft top layer makes it our most plush mattress. You get to sleep in alignment and let your back muscles rest. Hundreds of resilient springs add lift, airflow, and a bit of bounce. Its soft and inviting while still giving you the support your body needs. Size: King.