At the other end of the spectrum are the small, flat, genoa-like sails, like the Code Zero. Basically a reaching genoa, the foot lengths are shorter, at 150-165 percent of the J. The girths are in the 55-70 percent range, the shape is flat, and luff projection is minimal. Optimum apparent wind angles are usually 50-120. For this sail, fabric weight must be stronger. These sails often require specialized composite materials, as nylon has too much stretch.