Unidirectional fabrics have all the fibers running in a single direction. The main advantage of unidirectional material is its ability to control strength and stiffness in a specific direction. Unidirectional material is also usually thinner which allows for more control over laminate thickness and also reduces the likelihood of trapping voids or air bubbles. The disadvantages include longer time to laminate parts due to thinner plies, increased susceptibility to cracks that rapidly extend the length of the fiber, difficulty laminating complex curves without wrinkles and lack of aesthetic appeal.