SUP - Composite Boards
Composite SUPs are rigid designs as opposed to inflatable. Sometimes referred to simply as hard boards. They offer superior performance in almost every scenario, with the main penalty being storage and transportation. If you are serious about SUP, then composite is the way to go.
Constructions vary widely, and typically container a mix of materials wrapped around a foam core. High end boards are typically moulded and use a lot of carbon. This makes them very light. Glass fibre and other materials are used to reduce cost and change the characteristics of the board. Plastic shells are also used on thermoformed boards which are very durable.