Resins act as the support matrix for the fibers, impregnating them and forming the structure of the composite. Resins provide compressive strength and create adhesion between the fibers and laminate layers, while keeping the fibers in the correct position and orientation. Several types of resin are available, with the most commonly used being polyester, vinyl ester, and epoxy. They can be used in many different construction methods depending on the chosen process, with options including hand or wet lay-up, vacuum bagging, infusion, and RTM, or as pre-impregnated materials where the resin is already combined with the reinforcing fibers.