The spa shell will determine to a large extent the overall look, comfort, durability and cost of the spa.
Cast Acrylic reinforced with fiberglass: is beautiful, durable, and versatile and the most common material used for spas shells. A Fiberglass reinforced spa shell is extremely strong and can be molded into complex, contoured shapes for comfortable, form-fitting seating in a large range of sizes.
Cast Acrylic reinforced with a polymer substrate: provide the same durable acrylic surface, but are more flexible than fiberglass shells and require extra support.
All Plastic: plastic spa shells are made using a process called spin casting where plastic resin is heated up and the mold is rotated around letting the melted plastic form the shape of the spa shell.
Flexible vinyl: Vinyl spas are available as an inflatable or foam. They are extremely portable and can be easily moved and stored when not being used.