Casper Onyx 2.0 Split King Mattress with Head Up Only Base

Foam mattresses are naturally suited for adjustable bedding because of their inherent flexibility and resilience. This mattress features a triple-layer foam construction, including a firm Casper Core base and responsive Breathe Flex Foam. These materials are engineered to bend seamlessly with the RTG Sleep 2900 adjustable base without losing their structural integrity or causing permanent creasing, ensuring consistent support even when the head is elevated.

The split king design is specifically engineered for couples with different sleep preferences. Each side of the bed operates independently, allowing one person to sit up and read or watch TV using the head-up base while the other partner sleeps completely flat. To minimize the "gap" feel, this mattress uses a tight-top design and a cozy knit cover with added stretch, providing a smooth transition between the two sides while still allowing for independent movement.

Yes. Utilizing the head-up functionality of the included adjustable base can provide significant relief for those dealing with snoring or acid reflux (GERD). By elevating the head, you can help keep airways more open and use gravity to prevent stomach acid from rising. The wireless remote allows you to find the precise angle that provides the most relief while maintaining the pressure-relieving comfort of the Breathe Foam layers.

Absolutely. One of the primary lifestyle benefits of a split king setup is its modularity. Because a split king consists of two Twin XL mattresses and two separate bases, it is much easier to navigate through tight apartment hallways, elevators, or narrow staircases than a traditional, one-piece king mattress. This makes it an excellent choice for urban dwellers or those in multi-story homes where space for maneuvering large furniture is limited.

This mattress is obsessively engineered for both support and temperature regulation. The top layer of Breathe Flex Foam provides a responsive "bounce" that makes it easy to move, while the secondary Breathe Foam layer is perforated to promote constant airflow. All foams used are CertiPUR-US certified, meaning they are tested for low VOC emissions to ensure better indoor air quality, which is especially beneficial for health-conscious shoppers or those with sensitivities.

To ensure the mattresses can move independently without the sheets popping off, you will need a split king sheet set. This typically includes two Twin XL fitted sheets—one for each mattress—along with a single King-sized flat sheet and King pillowcases. For the best experience, our experts recommend using high-quality fitted sheets with deep pockets and strong elastic to accommodate the 10.5-inch mattress profile and the movement of the adjustable base.