The lancero is long and thin, usually with a ring gauge of about 38. Some have a pigtail cap. It is a parejo, but a specialized size. There is little room in the bunch, so ligero has to be used carefully, and the wrapper has a large effect on the flavor.
Lanceros take longer to roll and are easier to damage. Companies that still make them tend to treat them as a skilled specialty size rather than a high-volume size.
For the opposite shape, see the toro or the robusto. They can use the same tobacco in a different shape.
Full guide: lancero guide. Size chart: ring gauge and length cheat-sheet.