Advanced Support. Engineered to help common sleep problems, the Serta Perfect Sleeper Strathfield Firm Twin XL mattress will work to eliminate tossing and turning and give you the restful night’s sleep you deserve. Featuring high-performance heat and moisture-regulating fabric with an overall mattress design that helps promote airflow, this mattress offers a comfortable and balanced sleep temperature. Cool Twist Gel Memory Foam gently conforms to the body for enhanced cushioning, reducing uncomfortable pressure points. As an added bonus, Ultimate Edge Support strengthens the mattress edges, reducing the frustrating edge roll-off - giving you more room to stretch.