The large sail plans and raked bows of these vessels invite confusion with clippers, but there are significant differences. Clippers were optimized for speed, these vessels were optimized for cargo capacity and ease of handling. Most clippers were of composite construction (iron structure, wooden planking), full rigged and had a cargo capacity of less than 1,000 tonnes; these vessels were iron and steel hulled, usually barque rigged, and had far greater cargo capacities. Clippers had already begun to disappear when these vessels emerged.