Thanks to the brilliant innovation of the DURA-SHIELD®, Strong Spas’ HardCover model is the best in its class for durability. The DURA-SHIELD® uses patented technology to create a true HardCover molded hollow from durable resin, then it’s filled with proprietary foam to protect against harsh environments and provide energy-saving heat retention. Combining resilience with security, strength, and beauty, the HardCover requires little maintenance and is built to last.