Cove Spa shells are made of a thermoformed, matte finish, High Density Polyethylene (HDPE) which is the most indestructible shell material available in a portable spa. This durability, along with the beautiful matte finish in 10 colour options, makes it the product of choice for discerning buyers with value in mind. HDPE has a much greater tensile strength than acrylic, the plastic most other hot tub shells are made with. Cove Spa shells are so strong they do not have to be reinforced with resins and fiberglass like acrylic shells. Due to this strength, COVE Spa shells carry a 10 year Warranty!