Carbon fibre is composed of carbon atoms bonded together to form a long chain. The fibres are extremely stiff, strong, and light, and are used in many processes to create excellent building materials. Carbon fibre material comes in a variety of "raw" building-blocks, including yarns, uni-directional, weaves, braids, and several others, which are in turn used to create composite parts. The properties of a carbon fibre part are close to that of steel and the weight is close to that of plastic. Thus the strength to weight ratio (as well as stiffness to weight ratio) of a carbon fibre part is much higher than either steel or plastic. Carbon fibre is extremely strong. It is typical in engineering to measure the benefit of a material in terms of strength to weight ratio and stiffness to weight ratio, particularly in structural design, where added weight may translate into increased life cycle costs or unsatisfactory performance.